Một anh sinh viên thực hiện phép lai giữa hai dòng thuần chủng khác nhau (aaBBDD và AAbbdd) đã thu được một giống hoa có màu sắc xanh rất hiếm gặp. Để duy trì giống hoa đó, anh ta dùng phương pháp tự thụ phấn. Sau một số thế hệ, nhiều cây con trở nên yếu ớt, sức chống chịu kém.
a. Hiện tượng gì đã xảy ra ở các cây con? Nêu nguyên nhân của hiện tượng này.
b. Có bao nhiêu dòng thuần chủng mới có thể tạo ra từ phương pháp trên? Viết kiểu gen của các dòng thuần chủng mới.

Khí A thu được khi cho 87 gam MnO2 tác dụng với axit clohiđric đặc, dư. Dẫn A
vào 500ml dung dịch NaOH 5M (D = 1,25 g/lml), thu được dung dịch B. Tính nồng
độ phần trăm, nồng độ mol của các chất trong dung dịch B. Biết thể tích dung dịch
thay đổi không đáng kể.

1.The bloodstain on her dress was………………….. NOTICE
2.The hurricane caused terrible………….along the coast. DESTROY
3.The ring was not at all valuable: in fact, it was almost…………….. WORTH
4.I’m afraid there is going to be another…………..of the currency soon. VALUE
5.Th secretary was very busy all day dealing with …………… ENQUIRE
6. The teachers stressed the need for regular………………. ATTEND
7.Shara……..opened the door of the cellar, wondering what she might find. CAUTION
8.Distances which in …….timesbwould have taken months now only take a few hours.EARLY
9.Except for a few primitive communities, we all have become ……….to the aeroplane as part of
the world we live in. CUSTOM
10.The………….of the air has certainly brought great benefit to man. CONQUER
11.And yet in some ways it has proved………. HARM

12.For example, when we are…….by air we do not have the same opportunity to admire the
places we pass as we do by train or car. TRAVEL
13.This jewel is not simply valuable, it is ……… VALUE
14.Susan has two bad characteristics: jealousy and …….. POSSESS
15. the crowd showed its……….by shouting insults at the players. APPROVE
16. The policeasked him to give a…………of the suitcase he had lost. DESCRIPTION
17.He had no ………..that he was being watched. SUSPECT
18.This is Peter, my personal……………… ASSISST
19 Althogh I was positive that the girl had stolen my ring, I could not find any……. PROVE
20.Ther’s a …..at the Bristish Embassy tonight. RECEIVE
21That was a very…….thing to say. HURT
23.There is enough……..in the world without people making films about it. SAD
24.Has the doctor given you anything for your………. DEPRESS
25.It was with a certain amount of ……..that he left. RELUCTANT
26.He was too…….to tell his teacher about the stupid mistake. SHAME
27,Could you ……..the picture over the sofa? STRAIGHT
28.It’s hard to buy ,meat on the island but fish is………… PLENTY
29.My collegues are very pleasant, but the manager is alittle…… FRIEND
30.The ……..of those who have nowhere to live is ignored. MISERABLE
31.He was……….for three days after the accident. CONSCIOUS
32.The conditons in the men’s prison were………. HUMAN
33.He’s a bully,That’s why he’s so ……….with his school friends. POPULAR
34.She’s a very sweet child,very ………….indeed, not at all impolite lke her sister.LIKE
35.i can’t follow you.What you are saying is totally……………………… LOGICAL
36.Unfortunalely, the natural resources are becoming ……..for the support of the increasing
population. ADEQUATE
37.But the………..of natural resorses by artificial products is not always possible. PLACE
38.In biology, for example, the………of life in a test-tube is now a possibility. CREATE
39………..warfare is another danger made tenable by morden research. BIOLOGY
40.Thousands of people could be destroyed by using only a few……..germs. FATE
41.This leads to questioning the values of our present………. MORAL
42.Is the pursuit of ………still one of man’s most important aims? KNOW
43.We always have a bed ready in the spare room in case visitors arrive…….. EXPECT
44.That painting is not extremely valuable, it is…….. PRICE
45.to avoid……..on the journey we’d better pack these in either cotton wool or solf paper.BREAK
46.The government is going to hold a…………….to find out what the people really think about the
proposal. REFER
47,Make sure that you……the electricity before you start mending this light switch. CONNECT

48.It’s quite….to ask him again.he’ll never agree. POINT
49.The speakers showed his nervousness by constantly………his tie. STRAIGHT
50.Is there any difference between edoism and…………………….? SELF
51.it is dangerous for an………driver to drive a car in the centre of Paris during the mid-day rush
EXPERIENCE
52.After the death of her parents, Lisa was brought up in an……… ORPHAN
If you don’t put the proper stamps on the envelope, the…….willl have to pay double when he
receives the letter. RECEIVE
53.The cat looked at the new type of food on its plate ……….. SUSPECT
54…………………….his working life he has been dreaming of being able to retire on a farm.THROUGH
55.Tom gave the……..a pound . BEG
56.Poor Quentin put his head too far out of the raiway carriage window and was …….by a passing
train. HEAD
57.This is no longer a quite residential……………………………….. NEIGHBOUR
58.Ken gave the child a ……..of sweets. HAND
59.The discussion was brought to a ………..conclusion. SATISFY
60.Unlesss you measure with the greatest ……..the door will not fit properly and we shall have
trouble with it. ACCURATE
61.So many strikes are a great ……to the country’s economic recovery. HINDER
62.No, this is not an original; it’s a good ………though. PRODUCE
63.Peter, now that you’re the head of the family, you must take your…….place at the head of the
table. RIGHT
64.There is always a …….of fresh vegetables at this time of the year. SCARCE
65.He is interested in the ……of old buildings. PRESERVE
66.The manager handed in his ……..after being accused of dishonesty. RESIGN
67.All the newspapers praised the……..of the firemen. BRAVE
68.We can only catch criminals if we have the full …….of the general public. COOPERATE
69.She gave me a very……….look when she saw that I wasn’t wearing the correct uniform.
APPROVE
70.There’s a saying in English:”……..speak loader than words.” ACT
71.I don’t think Tom’s getting too much sleep lately.His eyes are terribly……… BLOOD
72.The Army tried unsuccessfully to…..the Government. THROW
73.Industry Robots work with far greater……. Than most men. PRECISE
74. Yet many people make no plans for this period of their lives and suddenly find
themselves……………. OCCUPY
75.And now they have all day in which to do the …..things they always said they never had time
to do before. NUMBER
76.If elderly people are really going to enjoy their leisure, then they must make proper…….for it..

PROVISION
77.The judge was caught……admiring himself in the mirror in his new wig. AWARE
78.his examination results were so unsatisfactory that it seemed……..for him to continue
studying. POINT
79.The ambulance-men carried the injured man into the hospital on a…… STRETCH
80.He bowed to the small girl with elaborate………. COURTEOUS
81.he was bound hand and foot and so was…..to escape. POWER
82.It is thoroughly dishonest and ……to cheat in an examination. HONOUR
83.They meet and shout and wave banners and applaud their………. LEAD
84.if trouble breaks out,they may be arrested and even ……….. PRISON
85.They frequently……….the traffic as they march through the streets. MOBIBLE
86.They cause trouble and…..to pedestrians and police. IRRITATE
87.With the result that people become …..to their cause. SYMPATHY
88.Therefore,many people who are badly-educated feel they are……. FAIL
89.More ………should be given to these people to continue their studies. COURAGE
90.otherwise much ……..can result from doing boring work. HAPPY
91.Many …..poeple are wasting their time in monotonous jobs. GIFT
92.Vietnam declared its……….in 1945. DEPEND
93.We are going to…………our school next year. LARGE
94.Their …………on the mountain was attributed to the warm clothes and the tent which they had
with them. SURVIVE
95.Switzerland is a ……….coutry. MOUTAIN
96.He is vey anxious about the ……of his passport. LOSE
97.The nineteenth-century faith in the power of science is now very…….. QUESTION
98.George made an usually ……..remark about his wife’s new dresss. COMPLIMENT
99.A person with an………complex can be very disagreeable . INFERIOR
100. He has put on his,……..as it is bitterly cold. COAT
101. There was loud……….as the clown fell off the ladder. LAUGH
102.I had to check the wages in…………to my normal work. ADD
103.Those berries are ……………..Don’t eat them. POISON
104.The lack of ……….at rents which the ordinary person can afford is a disgrace to the nation.
ACCOMMODATE
105.The …………of vast office blocks in our cities occupies valuable space that could be used for
homes. ERECT
106.Such blocks are frequently left……….. OCCUPY
107.This is because to convert such buildings into flats for lower-paid workers would be…….for
the property owners. PROFIT
108.The only answer is for local people to form housing…….to help themselves.ASSSOCCIATE

109.The problem, however, still remains of where they can find land ………..for development in
urban areas. SUIT
110. But the more noise there is, the more ……we seem to become to it . SENSE
111.We eat in café’s and restaurants to the …….of taped music. ACCOMPANY
112. We walj in streets where the noise of traffic is almost………. DEAF
113.At night we close our windows only to be kept…….by our neighbour’s radio or
television.WAKE
114.I was kept ,…………lastnight by the noise from a party in the flat above. WAKE
115.My wise is……….of spiders.
116An acroplane has to overcome the ………….of air. RESIST
117. Have you got some kind of……..on you? IDENTIFY
118.UFO means ………..Flying Object. IDENTIFY
119.NATION
- If he isn’t Spanish, What ……is he ?
-The coal industry was originally private but was……in the 1940’s.
-There ‘s no ………service in the United Kingdom.
120.OBSERVE
-it was very,……….of you to notice that.
This …….houses the largest telescope in the coutry.
He’s under ……all the time.
121.VARY
-The temperature is very………..at this time of the year.
- Do you like this new ……….of apple?
-There are…….desserts to choose from.
-politicians ………..blame the media if they don’t win the election.they’re so predictable.
122.CREATE
-I would like to show you my latest ……..,which I have called “Boats on a Lake”.
-The chameleon is a very strange……….
-Conan Doyle was famous as the ……..of the great detective,SheerlockHolmes.
123.CRITIC
- Why does everybody ……him all the time?
- After so much …………..he felt he had to resign.
-They were very ……..of his efforts to improve services.
124.DEMONSTRATE
-The……..all satdown in the middle of the road.
- He offered to give me a………….of how the machine worked.
125.DICTATE
--The boss wants you to take some……………………..

- he acted in an extremely………………manner,which made him very unpopular.

126.ADD
-Are all those …….they put in food really necsssary?
-In ,……….to doing the cleaning,I make the coffee.
127.ADMIRE
-This is an………………..piece of work.
-I am full of…………….. for the improvements he’s made.
128.ADVERTISE
-He works for an ………………….agency
-I saw an ………………………for the job in our local newspaper.
129.BASE
-My grandfather only had a very……..education.
-the organistion is run on a voluntary…………………………
130.CONFIRM
- She received a letter of ……….from the hotel.
-We’vve received an………………………..report of an exploitation outside the President’s house.
131.CONTINUE
-His latest book is a……………………of his previous one.
-The train service was………………….because it wasn’t used by many people.
132.It’s hard to find……………………in the summer. ACCOMMODATE
133.I had to write a……………..for homework. COMPOSE
134.there was a strange……………..in the bowl. MIX
135.Gardening is a relaxing…………………………..for some people, but not for me! OCCCUPY
136.Could I have………….to go home early? PERMIT
137.There are several…………..mistakkes in this letter. PUNCTUATE
138.I have made a ……………..for next weekend. RESERVE
139.he made a…………about the robbery. STATE
140.He’s having …………………for his bad back. TREAT
141.We must meet soon,……………….before Saturday. PREFER
142.the earthquake caused …………..damage. EXTEND
143.The road were…………….because of the snow. PASS
144.She took the job to be…………………………independent. FINANCE
145.He died under……………………………….circumstances. SUSPECT
146.We can look forward to a period of……………. PROSPER
147.I’m afraid this plan will prove very ………….. DEVISION
148.I’m afraid I rather………………..agreed to help. WISE
149.She spent hours getting the house…………..clean. SPOT

150.I don’t mind ……………………….criticism but there’s no need to be unpleasant. CONSTRUCT
151.If you have any special……………………,please let me know. REQUIRE
152.If you lose your cheque book , you should ………………the bank without delay NOTE
153.The …………of the flight was delayed so we had to spend the night at the airport.DEPART
154.The teacher warned the children that if they………..again, they’d be punished.BEHAVE
155.I’m afraid I’m in the …………….position of being out of work and heavily in debt. ENVY
156.Great works of art like the Mona Lisa are……………. PRICE
157.I’ve been a……………………since I had a heart attack. SMOKE
158.The weather in this country is so ………………that you never know what to expect.PREDICT
159.Although the stone in your ring looks like a diamond,I’m afraid it’s ……… WORTH
160.How can you …….the fact that some people live in mansions while others live in slums.JUST
161.We need her…………………….before we can go ahead. APPROVE
162.Have you got……….of your booking yet? CONFIRM
163.This time his ………………………were not believed. DENY
164.HE used the company for unfair…………………….. DISMISS
165.I hope to be a minister in the next………………… GORVERN
166. She made a thorough………..of the body. EXAMINE
167.his………………….definely needs working on PRONOUNCE
168.We were shocked by his ………..to see his son. REFUSE
169.i must clean this …………………..floor. DIRT
170.It was…………………….so they had to drive very slowly. FOG
171.Is lunch ready yet?they’re very………………….. HUNGER
172.Be careful.The roads are very……………………… ICE
173.I’d like a nice ……………….orange JUICE
174.Why do you give such …………………………….parties NOISE
175.his broken arm is still very………………………… PAIN
176.I live in the …………………..part of the coutry. SOUTH
177.He live in a……….house by the sea. WOOD
178.most orphans are bred in…………………………………… ORPHAN
179.Mrs Brown lived lonely in her……………………… POOR
180.Dicken’s novels were first ……………….in 1838 PUBLISH

1.Under her fine …….,circulation has increased by 100,000(EDIT)
2.It’s pure…..there’s no evidence to support these allegations at all (HEAR)
3.The factory’s closure will have far –reaching ……for the whole region(IMPLY)
4. There’s a/an …….rule in this office that we all go out for a drink together after work on
a Friday.(WRITE)
5.In formalwriting, it is unusual to make use of the …..mark to express
surprise.(EXCLAIM)
6. You are ….forbidden to use a calculator in this examination.(express)
7. The chances against this kind of unusual……..are very high.(OCCUR)
8.I’m not convinced that there’s a…..link between pollution and global warming(CAUSE)
9. The….of the cliffs by the sea has completely changed the landscape.(ERODE)
10.Female animals have an ……need to protect their young(instinct)
11.The police are investigating the………disappearance from the zoo of a number animals
(MYSTERY)
12.We knew that getting between the whaleand the ship was…..,but it was the only way
to stop them hunting.(RISK)
13.what’s your…of the situation?(ASSESS)
14. We have to wait for ……conditions to launch the boat(FAVOUR)
15.The expedition travelled miles in search of the ……mountain gorilla.( elude)
16.Following the ……of the volcano,hundred of villages were destroyed.(erupt)

1.Our next door neighbour is a who is studying marine life BIOLOGY
2. Laura has been very during my illness. SUPPORT
3. My main at home is to wash the dishes. RESPONSIBLE
4. Tam usually helps her mother with chores. HOUSE
5. Ms.Hunltley is a very warm and person. CARE
6. If you are worried about their put your jewels in the hotel safe. SECURE
7. What I am telling you is strictly CONFIDENCE
8. They’ve enough toys to keep them out of for a while. MISCHIVOUS
9. We were relieved that Tom had arrived at the wedding dressed. SUIT
10. Remember you are in the army! If you orders you’ll get a court martial. OBEDIENT.
11. By doing well at school, he hoped to win his parents’ . APPROVE
12. The Western people are very concerned with phisical when choosing a wife or a husband.

ATTRACT
13. Vienna is a real centre for music lovers. CULTURE
14. Would you like to go to our wedding? The takes place at St John’s church. MARRY
15. David and Mary have been in for five years. PART
16. The police are intrerested in the sudden of the valuable painting. APPEAR
17. In our country it is for the bridegroom to make a speech. TRADITION
18. Micheal has just got to a girl he’s has known since he was a boy. ENGAGE
19. Almost young Americans want to lead lives. DEPEND
20. Each member of our group has a of opinion. DIVERSE
21. The restaurant manager was very and said we could have APOLOGY
our meal for free.
22. They were having an about the children. ARGUE
23. Julia dances a lot more than all of her friends. MARVEL
24. The of the heating system requires several days. INSTALL
25. He was very pupil and seemed to spend most of the time ATTEND
looking out of the windows.
26. The girl sitting next to Mike smiles very doesn’t she? ATTRACT
27. Mr. Andrew enjoys with his students after class. SOCIAL
28. At first he was rude, but later he apologised for his . POLITE
29. The atmosphere was very and everyone was on first name term. FORMALITY
30. The shop seemed to spend most of the time talking rather than attending to the sustomers. ASIST
31. In Britain education is between the ages of 5 and 16. COMPEL
32. Work experience is an important experience for young people. EDUCATION
33. The between public and private school system in many countries is quite clear. DIVIDE
34. The lecturewe heard last night was very . INFORM
35. The written English is not phonetic, which causes difficult for foreigners. SYSTEM
36. The strike caused widespread to train services. DISRUPT
37. It is not always easy to earn a living as an ART
38. The British government the railways in 1948. NATION
39. The whole trip to Africa was planned with precision. MATHEMATICS
40. He talks so much because he is a . POLITICS
41. ! You are offered the position. CONGRATULATE
42. Try not to be too if you do not get the job . APPOINT
43. It can be when preparing for the job interview. STRESS
44. His advice helped me create a good on my interviewer. IMPRESS
45. Remember to bring the letters of form your teachers. RECOMMEND
46. You should show when the job is explained to you. ENTHUSIAST
47. Always show your best side, you to work. KEEN
48. An is the person who answers the questions in an interview. INTERVIEW
49. My cousin has been working as an for over twelve years. ACCOUNT
50. I want to become a writer so that I can create characters and events. IMAGINE
51. If we don’t on electricity, there will be power cuts. ECONOMY
52. There is not anyone living in the island; it’s an island. INHABIT

53. There used to be a of schools, hospitals in my country. SHORT
54. We believe that we will gain great and build better life for our people. ACHIEVE
55. Only a support the new Enterprises Law. MINOR
56. The new laws have both domestic and foreign private investments. COURAGE
57. Vietnam has substantial changes since Doi Moi. GO
58. The National Congress of the Vietnamese Communist Party continued to reaffirm its to Doi Moi.

COMMIT
59. I couldn’t get much work done as I was being interrupted by people telephoning me.

CONTINUE

60. Every effort was made to return the purse to its owner. RIGHT
61. We are really about the peace process in the region. OPTIMISM
62. People believe that he was killed by a group of . TERROR
63. The earth is being by pollution. THREAT
64. As the child’s head went under the water for the third time, I stood and watched to help. I can’t swim.

POWER

65. In the future cars can run on anything from to methane gas. ELECTRIC
66. I’m afraid you’ll have to see Mr.Pound. All matters concerning finance are his RESPONSE
67. Although she arrived , we made her welcome just the same. EXPECT
68. Tom fell into a deep on hearing the news. IMPRESS
69. He was very sad because he was told that his best friend got an disease. CURE
70. I’m sorry I haven’t phoned. I’ve been busy this week. CREDIBLE
71. The desert is in the part of the country. SOUTH
72. They led a expedition across the sand dunes in 1930. SCIENCE
73. The police are still looking into the disappearance of the chief cashier shortly after the bank robbery.

MYSTERY

74. The Sahara desert is the desert in the world. LARGE
75. It’s the most film I’ve ever seen. FRIGHT
76. There are very few places on earth today. Man has been nearly everywhere EXPLORE
77. The path to the village will be by the local government. WIDE
78. There are types of dunes in the Simpson desert. DIFFER
79. They have decided to organise the election by the end of this year. PRESIDENT
80. Many efforts have been made to the national economy. STABLE
81. Smoking during pregnancy can the baby’s health DANGER
82. My only means of was my driver’s licence. IDENTIFY
83. I have read the guilines on the controlled of ocean resources. EXPLOIT
84. and overpopulation are the two big problems in the developing countries. FOREST
85. Many small towns in our country have been in the past few years. URBAN
86. There are only two in the air crash. All the other passengers were killed. SURVIVE
87. The Red List has been introduced to raise people’s of conservation needs. AWARE
88. Governments have enacted laws to protect wildlife from trade. COMMERCE
89. Scientists have many theories about how the universe first came into . EXIST
90. A is a person who studies plans or animals, especially outdoor. NATURE
91. Vehicles of over 3 metres in pay an additional toll. LONG
92. There is no need tobe so . I just asked how to get to the bus stop. DEFEND
93. Tyson nocked his out in the first round. OPPOSE
94. We stood and watched the dancers’ graceful . MOVE
95. I would like to show you my lastest , which I have called “Sound of Nature”. CREATE
96. The player didn’t agree with the refree’s . DECIDE
97. I hate playing badminton with Tom. He’s too . COMPLETE
98. I prefer scuba-diving to water polo because it is . ADVENTURE
99. Do you know when synchronized swimming first received major ? PULIC
100. After four hours’ typing I had a terrible headache. CONTINUE
101. The show was so that nobody knew who was coming on next. ORGANIZE
102. One of the aims of the organization is to provide aid to the refugees. HUMAN
103. Why don’t you take the and arrange a meeting? INITIATE

104. After some one of the children began to speak. HESITATE
105. International Red Cross has its in Geneva, Switzerland. HEAD
106. After the tsunami many people lost their families, friends and . LIVE
107. The driver of the lorry sustained only minor to legs and arms. INJURE
108. Was the of international Red Cross inspired by a Sweden? FOUND
109. The dotor gave him and injection to the pain. DIE
110. The mother was to see her son eating properly again. RELIEF
111. , there were five countries founding the Association of Southest Asian Nations.ORIGIN
112. The main goal of the association is to promote peace and in the region and all over the world.

STABLE

113. She was the only visitor into the sick room. ADMISSION
114. The two sides are engaged in the discussion. ACT
115. On my salary we have to live as as possible. ECONOMY
116. Don’t Peter. He’s a skillful campainer. ESTIMATE
117. In the past few years this area has become heavily . INDUSTRY
118. I think there are differences in every country. REGION
119. A of factors may be responsible for the increase in canser. COMBINE
120. They have agreed to provide assistance for countryside schools. FINANCE

Trong mặt phẳng, kẻ 2022 đường thẳng phân biệt sao cho không có hai đường
thẳng nào song song và không có ba đường thẳng nào đồng quy. Tam giác tạo bởi ba
đường thẳng trong số các đường thẳng đã cho gọi là tam giác đẹp nếu nó không bị đường
thẳng nào trong số các đường thẳng còn lại cắt. Chứng minh rằng số tam giác đẹp không
ít hơn 674.

\(\left\{{}\begin{matrix}x+y+\frac{1}{x}+\frac{1}{y}=\frac{9}{2}\\xy+\frac{1}{xy}+\frac{x}{y}+\frac{y}{x}=5\end{matrix}\right.\)

Cho các số thực a, b, c khác 0 thỏa mãn 2ab+bc+2ca=0. Tính giá trị của biểu thức:

\(A=\frac{bc}{8a^2}+\frac{ca}{b^2}+\frac{ab}{c^2}\)