They have been skating __________.
| A．for three hours | B．since three hours ago |
| C．three hours ago | D．since three hours |
The number of the cranes is getting ___________．If we don’t help them, they will disappear ___________ a few years．
| A．fewer and fewer; in | B．larger and larger; after |
| C．more and more; after | D．smaller and smaller; in |
We were swimming in the lake _______ suddenly the storm started.
| A．until | B．while | C．when | D．before |
The price of petrol(汽油) is not _______ that of last year, so some more people are planning to buy cars.
| A．as expensive as | B．so cheap as |
| C．as low as | D．so high as |
Everybody should study hard. No one can _______ us _______ a good future.
| A．provide; for | B．provide; with |
| C．keep; / | D．protect; to have |
There’s water all over the kitchen. You’d better _______ right away.
| A．to mop up it | B．to mop it up |
| C．mop it up | D．mop up it |