Mary really hard on his book and thinks he’ll have finished it by Friday.
| A．worked | B．has been working |
| C．had worked | D．has worked |
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 |
With temperature ______ so rapidly, we could not go with the experiment．
| A．fall | B．falling | C．fallen | D．to fall |