13. In order to _____ the development of the west of our country, many special policies have been made, such as encouraging people to go to work in the west.
| A．accelerate | B．accomplish | C．acknowledge | D．Accompany |
After the age of 50 people often _____________ their individual ambitions.
| A．desert | B．give in | C．give away | D．abandon |
He is a key ____________ in the murder so we must protect him from all kinds of danger.
| A．witch | B．watcher | C．wizard | D．witness |
Russia is _________ on the north of China.
| A．bounded | B．bound | C．boundary | D．lied |
Lately some scientists are experimenting ___________ white mice to ____________ this kind of medicine.
| A．on,try on | B．with, test on | C．on ,test out | D．with,carry out |
When the reached the top of the hill ,they _______________ so they had to stop for a rest.
| A．held their breath | B．out of breath | C．lost their breath | D．breathed deeply |