_____ is known to all, the age _______ children can go to school is seven.
| A．What; which | B．It; when | C．As; at which | D．Which; when |
The headmaster was dismissed three months ago.The post is too important to leave __________ any longer,especially before the college entrance examination.
| A．alone | B．away | C．vacant | D．occupied |
There are a lot of computers in the lab,and they need professional __________ to make sure they can be in a good state.
| A．operation | B．maintenance | C．service | D．advice |
He is __________ every day.He has never been late for school.
| A．busy | B．diligent | C．careful | D．punctual |
Universities have to provide student __________ for first-year students.
| A．adjustment | B．qualification | C．commitment | D．accommodation |
The space walk will last six and a half hours and the repair of Discovery is expected to __________ a little more than an hour.
| A．take | B．cost | C．spend | D．adjust |