We should return the books to the library time.A. aboutB. onC. byD. for

问题补充：

We should return the books to the library time.

A. about

B. on

C. by

D. for

答案：

A. about

(答案→)B. on

C. by

D. for

解析：我们把图书归还给图书馆按照常理应该是准时或按时归还，on time表示此意，

故选B。