30． the people have become masters of their own country that science can really serve the people.
| A．Only then | B．It is only when | C．Only when | D．It is only then |
Michelle found a job as a high school teacher which ________ spending quite a lot of time with students.
| A．enjoys | B．involves |
| C．practices | D．suggests |
When the group discussion is nearing its end，make sure to ________ it with important points.
| A．conclude | B．lead |
| C．avoid | D．hold |
If you are in trouble，Mike is always willing to ________a hand.
| A．lend | B．shake |
| C．wave | D．want |
The watch was very good，and he ________ 20 percent down for it.
| A．paid | B．cost |
| C．bought | D．spent |
Try not to cough more than you can________since it may cause problems to your lungs.
| A．check | B．allow |
| C．stop | D．help |