The cancer risks _______ with smoking have been well proved.
| A．combined | B．related |
| C．associated | D．caused |
Would you be kind enough to help the boy _____ Chinese is really hard to learn?
| A．who | B．whose | C．for whom | D．from whom |
_____ 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 |
—How did you like the concert last night ?
—I enjoyed it very much, but the dancers _____ a better job．
| A．could have done | B．must have done |
| C．could do | D．had done |
I appreciate _____ the opportunity to work in your company two years ago．
| A．giving | B．to give |
| C．being given | D．to be given |
_____ economic, political and cultural differences, it is difficult for China and America to fully understand each other．
| A．Apart from | B．Regardless of |
| C．On account of | D．In terms of |