Without the 
air to hold some of the sun’s heat, the earth at night ____ for us to live.
| A．would be freezing cold | B．will be freezing coldly |
| C．would be frozen cold | D．can freeze coldly |
The job was a great challenge and the bad weather _________ our difficulties．
| A．added to | B．added | C．added up to | D．added in |
It is said that this is the biggest lab ________ they have ever built in their school.
| A．which | B．what | C．不填 | D．where |
In order to attract more customers, many supermarkets usually sell their goods at a good________ at weekends.
| A．benefit | B．discount | C．interest | D．cost |
It will be at least three weeks________ he recovers from his illness and returns to work.
| A．before | B．when | C．since | D．after |
He found his house broken into and many things stolen _______ his return from office.
| A．with | B．in | C．at | D．on |