C₂H₂ → X → Y → m-bromnitrobenzen.

Các chất X và Y lần lượt là

A. benzen; nitrobenzen

B. benzen; brombenzen

C. nitrobenzen; benzen

D. nitrobenzen; brombenzen

- Đi học đg h

- Làm bài và thuộc bài trc khi đến lớp

- Chăm chú nghe giảng

-....

Choose the best answer:

Up to the present, George __________ good work in his class.

A. does 

B. is doing 

C. has done          

D. had done

Mark the letter A, B, C, or D on your answer sheet to indicate the underlined part that needs correction in each of the following questions.

The occean probably distinguishes the earth from other planets of the solar system, for scientists believe that large bodies of water are not existing on the other planets.

A. probably

B. for

C. are not existing

D. from