On his way to the airport，it ________him all of a sudden that he had forgotten his passport.
| A．hit | B．knocked | C．occurred | D．beat |
As we grow older,we learn theof our abilities.
| A．heights | B．scores | C．limits | D．lengths |
1．! There is a train coming．
| A．Look out | B．Look around |
| C．Look forward | D．Look on |
9.―Your job ____ open for your return.
―Thanks.
| A．will be kept | B．will keep |
| C．had kept | D．had been kept |
8.Customers are asked to make sure that they ____ the right change before leaving the shop.
| A．will give | B．have been given |
| C．have given | D．will be given |
7.Although the causes of cancer ____， we do not yet have any practical way to prevent it.
| A．are being uncovered | B．have been uncovering |
| C．are uncovering | D．have uncovered |