28．You ______ very fast if you went from New York to Boston in six hours．
| A．should drive | B．would have driven |
| C．may drive | D．must have driven |
There's no way of knowing why one man makes an important discovery________another man，also intelligent，fails.
| A．since | B．if | C．as | D．while |
It was a real race________time to get the project done.Luckily，we made it.
| A．over | B．by | C．for | D．against |
A serious study of physics is impossible________some knowledge of mathematics.
| A．against | B．before | C．beyond | D．without |
I have an appointment ________ Dr.Smith, but I need to change it.
| A．to | B．off | C．with | D．from |
________everyone here，I wish you a pleasant journey back to your country.
| A．By means of | B．On behalf of |
| C．In search of | D．For fear of |