---What do you think of your parents?
---They always let me do ________ I think I should do.
| A．when | B．that |
| C．how | D．what |
When the man came in, gun in hand, we all stood there, ________．
| A．astonished | B．astonishing |
| C．being astonished | D．having astonished |
If nature does not provide man with the necessary material, it is the laboratory ____ he will turn to for it．
| A．where | B．that | C．which | D．what |
By the time you have completed the essential training, you _____ exposed to virtually every new feature of the course．
| A．are | B．will have been | C．have been | D．will be |
_______ more to be pitied than blamed．
| A．Uneducated are | B．Uneducated is |
| C．The uneducated are | D．The uneducated is |
Earth is believed ______ by an object the size of Mars at some point in the distant past
before its surface cooled．
| A．to be hit | B．to have hit | C．to have been hit | D．to hit |