_____ in the library regulations that any book borrowed be returned by due time, or the borrower will be fined．
| A．What is required | B．It is required |
| C．As is required | D．Which is required |
24．The policemen_______the stolen place again and again，and finally they found the evidence who stole the antique（古董）．
| A．got through | B．picked up | C．went over | D．turned over |
23．What the boss really doubts is__________his employees will go on working in the company．
| A．that | B．weather | C．when | D．whether |
32. His composition won first prize, ______ made him too happy to sleep for nights.
| A．what | B．that | C．which | D．Where |
31. We are waiting ______ for your absence.
| A．your explanation | B．to have your explanation |
| C．about your explanation | D．having your explanation |
30. With little knowledge about the area he succeeded ______ many researchers failed.
| A．the place where | B．in place | C．while | D．Where |