Polar bears live mostly on __________ sea ice, which they use as __________ platform for hunting seals.
| A．a; a | B．a; the |
| C．不填; a | D．the; 不填 |
That year his total income, with his reward ________， ________ 12, 000 yuan.
| A．added to; added up to | B．added; added to |
| C．added up to; added | D．adds to; adds up to |
---Do you still remember when we went to Chong qing?
----I can’t remember now but_____ sometime last summer?
| A．could it be | B．might it be | C．must it have been | D．could it have been |
The demand that the law on gun ownership _____ be changed ___ is very strong.
| A．changes | B．will be changed | C．be changed | D．be changing |
The increase of the number of the students makes the limited computers not ________ to each student.
| A．available | B．helpful | C．acceptable | D．affordable |
He had just sent an email to his pal on the Internet ________ the system broke down.
| A．while | B．when | C．after | D．since |