Câu hỏi: 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 1: 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 2: This apprentice has spent two weeks to work on that new machine.

A. has spent

B. to work

C. on

D. new machine

Câu 3: 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 4: Conservation is the safeguarding and preservation of nature resources.

A. is

B. safeguarding

C. preservation

D. nature

Câu 5: The deadbolt is the best lock for entry doors because it is not only inexpensive but installation is easy.

A. the best

B. because

C. not only

D. installation is easy

Câu 6: The mother asked her son if he would have the floor clean the day before.

A. asked

B. if

C. would have

D. clean