Câu hỏi: How long have they been working _____________ the company?

A. for

B. at

C. in

D. on

Câu 1: He insisted ______ taking us dinner.

A. on

B. in

C. over

D. of

Câu 2: Ed depends ________ his family for financial support.

A. on

B. in

C. of

D. at

Câu 3: Our study is very important____________ our future and useful_____________ our country.

A. for/ for

B. to/ to

C. for/ to

D. to/ for

Câu 4: She always takes good care _______ her children.

A. for

B. in

C. of

D. with

Câu 5: We congratulate you ___________ your successful flight.

A. on

B. about

C. by

D. with

Câu 6: The pens made___________ plastic are very cheap.

A. by

B. with

C. of

D. to