Life is like a long race _____ we compete with others to go beyond ourselves.
| A．why | B．what | C．that | D．where |
It's not easy to change habits，________ with awareness and self－control，it is possible.
| A．for | B．or | C．but | D．so |
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 |