Chất hữu cơ X có công thức phân tử C₈H₁₅O₄N. Khi chó chất X tác dụng với dung dịch NaOH, đun nóng, thu được sản phẩm gồm chất Y, C₂H₆O và CH₄O. Chất Y là muối natri của α-amino axit Z (chất Z có cấu tạo mạch hở và có mạch cacbon không phân nhánh). Số công thức cấu tạo phù hợp của chất X là

A. 2.

B. 3.

C. 4. 

D. 1.

Wow, what a beautiful picture! It attracts my attention from the first sight -> at first sight. As you can see, this picture describes the view of natural -> nature. The weather is very nice, the air seems fresh and the view looks very beautiful. In the picture, there are many planes and some flowers coloured red ( or some red flowers), and there is an artist who is drawing the butterfly on his hand and is holding a pen to draw. That artist is wearing a round glass to look everything better. He has a silver spotted beard, a nice watch and he is wearing a blue shirt. The butterfly whose wings are long, colour white and black on the top with head and long ears is perching on a white flower. Có thể thêm: This is the most beautiful scene that I have ever seen./ It's so wonderful!

Phát biểu nào sau đây đúng?

A. Hỗn hợp tecmit (dùng để hàn gắn đường ray) gồm bột Fe và Al₂O₃

B. Thành phần chính của quặng boxit là Al₂O₃.2H₂O

C. Nước cứng là nước chứa nhiều ion HCO₃^-, SO₄^2-, Cl^-

D. Các kim loại kiềm thổ đều cùng kiểu mạng tinh thể lập phương tâm diện

Gọi phân số cần tìm là \(\frac{x}{y}\)

Ta có: \(\frac{51}{68}=\frac{4}{3}\)

\(x=15:\left(4-3\right)\times4=60\)

\(y=15:\left(4-3\right)\times3=45\)

Vậy phân số cần tìm là \(\frac{60}{45}\)

1. Julia said that she_______________there at noon.

       => B. was going to be ( Câu gián tiếp -> Verb phải lùi một thời)        

2. He_____that he was leaving way that afternoon.

A. told me         

B. told to me ( tell sb , không phải là tell to sb)        

C. said me  ( đúng thời nhưng phải là said to me)       

D.says to me ( đúng cấu trúc nhưng sai thời)

3. She said to me that she_________to me the sunday before.

A. wrote   (sai thời)      

B. has written   ( sai thời)      

C. was writing    ( sai thời)

D. had written

4. I_____________him to sell that old motorbike.

A. said to (Nghĩa không hợp lý)

B. suggested ( chỉ có 2 dạng suggest + that + clause hoặc suggest + v-ing )       

C. advised  ( hợp nghĩa và advise sb + to V)       

D. recommended ( không hợp nghĩa, recommend sb + sth)

5. My parents reminded me________the flowers.

A. remember to plant  ( sai cấu trúc, sai nghĩa)      

B. plant   ( remind sb + to V)      

C. to plant         

D. planting (sai cấu trúc)

6. I asked Martha____________to enter low school.

A. are you planning         

B. is she planning         

C. was she planning         

D. if she was planning ( xem cách dùng của câu gián tiếp nhé!)

7. Nam wanted to know what time___________.

A. does the movie begin (sai thời, sai ngữ pháp)        

B. did the movie begin (sai ngữ pháp)        

C. the movie begins  ( sai thời)       

D. the movie began

8. I wondered____________the right thing.

A. whether I was doing         

B. if I am doing ( sai thời)        

C. was I doing  ( sai ngữ pháp)        

D. am I doing ( sai ngữ pháp)

9. The scientist said the earth__________the sun.

A. goes round         

B. is going around         

C. went around         

D. was going around

10. Peter said that if he________rich, he_______a lot.

A. is-will travel         

B. were-would travel         

C. had been-would have travelled         

D. was-will travel

11. They said that they had been driving through the desert______________.

A. the previous day         

B. yesterday         

C. the last day         

D. Sunday previously

12. He asked the children____________too much noise.

A. not to make         B. not making         C. don't make         D. if they don't make

13. The man said that money____________the passport to everything.

A. will be         B. is         C. was         D. can be

14. The teacher said Columbus___American in 1942.

A. discovered         B. had discovered         C. was discoverring         D. would discover

15. John said he_______her since they________school.

A. hasn't met-left         B. hadn't met-had left         C. hadn't met/ left         D. didn't meet-has left

Part 4: 

We have seen photographs of the whole earth taken from great dis­tances in outer space. This is the first time, the (131) very first time, in man's long history that such pictures have been possible. (132) For many years most people have believed that the earth was ball-shaped. A few thought it was round and (133) flat, like a coin. Now we know, beyond doubt, that those few were (134) wrong/mistaken. The photographs show a ball-shaped (135) earth/planet, bright and beautiful. In colour photographs of the earth, the sky is as (136) black as coal. The (137) sea looks much bluer than it usually does to us. All our grey (138) clouds are a perfect white in colour; because, of course, the (139) sun is for ever shining on them. We are (140) lucky to live on the beautiful earth