Câu hỏi: Ecologists are trying to preserve our environment for future generations by protecting the ozone layer, purifying the air, and have planted the trees that have been cut down.

A. to preserve

B. for

C. the ozone layer

D. have planted

Câu 1: Conservation is the safeguarding and preservation of nature resources.

A. is

B. safeguarding

C. preservation

D. nature

Câu 2: It has ever been told that teaching is one of the more noble careers.

A. has ever been

B. is

C. the 

D. more noble

Câu 3: Before went abroad, he had finished his English course at the English-speaking Center.

A. went

B. abroad

C. had finished

D. English-speaking

Câu 4: What happened in New York were a reaction from city workers, including firemen and policemen who had been laid off from their jobs.

A. What happened

B. were

C. including

D. their

Câu 5: The chief of police demanded from his assistants an orderly investigation, a well-written report, and that they work hard.

A. The chief

B. from

C. orderly

D. that they work hard

Câu 6: Abraham Lincoln was a good president and was self-educated, hard working and always told the truth.

A. a good president

B. self-educated

C. hard working

D. always told the truth