Khi nói về sự hình thành loài mới bằng con đường địa lí, có bao nhiêu phát biểu sau đây đúng?

   I. Là phương thức hình thành loài có ở cả động vật và thực vật.

   II. Cách li địa lí là nhân tố tạo điều kiện cho sự phân hoá trong loài.

   III. Điều kiện địa lí là nguyên nhân trực tiếp gây ra những biến đổi tương ứng trên cơ thể sinh vật.

   IV. Khi có sự cách li địa lí thì sẽ nhanh chóng hình thành loài mới.

A. 1

B. 2

C. 3

D. 4

34a−4a=1320

\(\Rightarrow\frac{3}{4a}-\frac{16}{4a}=\frac{13}{20}\)

\(\Rightarrow\frac{3-16}{4a}=\frac{13}{20}\)

\(\Rightarrow\frac{-13}{a}=\frac{13}{20}\)

\(\Rightarrow\) (-13) . (20) = 13a

\(\Rightarrow\) a = - 20

V. Fill each blank with a word from the box.
1. What _______did _________ you do last Sunday?

2. I stayed at home and looked _________after_______ my younger brother

yesterday.
3. He lives in a small village in the mountains so he never _______feels_________worried about traffic jams.

4. You should remember to walk _______across_________ the streets at the zebra crossings.

5. Does your bike ever ________ ride________ down on the way to school?

6. We must always obey traffic _______rules_________ for our safety.

7. How far is _______it_________ from your house to the bus stop?

8. There did not use to be many vehicle on the roads in my hometown.

9. He used to break a tricycle when he was three years old.

10. Now there are more traffic accidents than there used to be in this city.

VIII. Make sentences using the words and phrases given.
1.Another problem is the increase in the number of cars on the road

2. There are transport rules but many people don’t seem really interested in following them.
3.The traffic is worst during rush hours when everyone is trying to get to work or get home
5. The traffic can be a nightmare for visitors to Viet Nam for the first time.
6. More people own private cars and it makes the problem of the traffic jams become worse.

7. Pedestrians can get injured or hit easily when they walk on the pavements or cross the roads at such times
8. Road users become very impatient or quite aggressive, constantly using their horns or
even shouting at others.

9. Three or four people on one motorbike is a common sight, particularly with young people.
10. Some people install air horn on their motorbikes, and this is really annoying for other
people and sometimes it causes accidents. .IX. Complete the second sentence so that it has a similar meaning to the first.
1. Did you often go to the beach when you lived in Nha Trang?
Did you use to go to the beach when you lived in Nha Trang ?
2. Linda doesn’t live with her parents any more.
Linda used to live with her parents.
3. I don’t have time to collect stamps as when I was in primary school.
I used to have time to collect stamps when I was in primary school.
4. He is not a poor man any more, but he becomes a rich businessman.
He used to be a poor man , but now he becomes a rich businessman
5. They didn’t often go to the cinema every Sunday last year.
They didn’t use to go to the cinema every sunday last year
6. My hair now is much longer than that in the past.
In the past my hair used to be shorter
7.I used to stay up late to watch football matches last year
8. There were some trees in the field, but now there aren’t any.
There used to be some trees in the field.

\(\frac{x+4}{2012}+\frac{x+3}{2013}=\frac{x+2}{2014}+\frac{x+1}{2015}\)

\(\Rightarrow\left(\frac{x+4}{2012}+1\right)+\left(\frac{x+3}{2013}+1\right)=\left(\frac{x+2}{2014}+1\right)+\left(\frac{x+1}{2015}+1\right)\)

\(\Rightarrow\frac{x+2016}{2012}+\frac{x+2016}{2013}=\frac{x+2016}{2014}+\frac{x+2016}{2015}\)

\(\Rightarrow\frac{x+2016}{2012}+\frac{x+2016}{2013}-\frac{x+2016}{2014}-\frac{x+2016}{2015}=0\)

\(\Rightarrow\left(x+2016\right)\left(\frac{1}{2012}+\frac{1}{2013}-\frac{1}{2014}-\frac{1}{2015}\right)=0\)

Vì \(\frac{1}{2012}+\frac{1}{2013}-\frac{1}{2014}-\frac{1}{2015}\ne0\) nên x + 2016 = 0

=> x = - 2016

want

1.Don't be silly!That........................ posibly be Rivaldo!

a)mustn't b)shouldn't c)won't d)can't

2.No sooner had we started the game,................ it began to rain.

a)than b)then c)that d)and

3.I................. be interested in playing badminton as a child.

a)could b)ought to c)might d)used to

4.They've told you time and time.................. not to go out at night.

a)to b)over c)again d)before

5.Sorry I'm late, but I ............................ feed my little son before leaving home.

a)needs b)must c)had to d)was to

6.Smith writes very quickly. He's.............................. finished his essay.

a)already b)been c)for d)yet

7. What are you going to do?-I don't know. I haven't made................... my mind yet.

a)on b)at c)in d)up

8.I've........................ to Paris. I went there in March.

a) been b)gone c) just d)yet

9.What did the girl say......................?

a)at you b)for you c)you d)to you

Ta có : x - 1 + x - 2 + x - 3 + ...+ x - 19 + x - 20 = - 619

(x + x +x + ...+ x ) + ( - 1 - 2 - 3 - ...- 20) = - 619

20x + (-210) = -619

20x = -619 + 210

20x = - 409

x = -20,45

Bạn đó cắt đi:

10 x 1/3 = 10/3 m

Phần còn lại là:

10 - 10/3 = 20/3

Đổi 5m = 15/3 m

Cách : Ta lấy đoạn dây 10/3 m đó gấp đôi lại thành 2 phần bằng nhau

Lúc đó mỗi phần dài: 10/3 : 2  = 5/3

Ta để đoạn 20/3 m và 5/3 để cắt phần dư và phần dư đó là: 15/3 m = 5m

I put the words in the correct from

1 is mr.ha a businessman?

2 our new classmate ,lan learns english very well

3 i don't like this chair.It's uncomfortable

4 hoa is having a medical check-up

5 it's sunny today in ha noi

II fill in each gap with a suitable preposition

1. i'm reading a book about history of china

2. it is far from your house to the school

3.the shirt looked beautiful.I tried it on but it didn't fit

4.john's worried about his final exam

5. what's ho chi minh city famous for ?

6. her sister is working in a computer company

7. can i talk to you for a moment?

8. my aunt sliced the beef into thin strips

III fill in each blank with the correct form of the word given in capital

1/hoa is having a medical check-up

2/in the countryside,people ofter know all the people in their neighbourhood

3/ you must be careful when playing video games beause they can be addictive

4/ i'd like a nice juicy orange

5/edison's most famous invention was the electronic bulb

6/this dictionary is very useful for you to learn english

7/ i have less time to play than my friends

Giải

Phân số cuối cùng là phân số duy nhất có mẫu chứa thừa số 2 với số mũ cao nhất là 2³. Khi quy đồng mẫu thì mẫu số chung là một số mà chia hết cho 2³ , các thừa số phụ đều chia hết cho 2 trừ thừa số phụ của phân số cuối cùng . Do đó tổng các tử mới không chia hết cho 2 mà mẫu mới lại chia hết cho 2

=> A không phải là số tự nhiên .