I____ my homework at nine o'clock last Sunday morning.
| A．am doing | B．was doing |
| C．do | D．did |
If I hadn't been faced with so many barriers，I ______ where I am．（ ）
| A． |
won't be |
B． |
wouldn't have been |
| C． |
wouldn't be |
D． |
shouldn't have been |
There will still be lots of challenges if we are to ______ garbage in a short time．（ ）
| A． |
clarify |
B． |
justify |
C． |
satisfy |
D． |
classify |
Instead of getting down to a new task as I ______， he examined the previous work again．（ ）
| A． |
had expected |
B． |
have expected |
| C． |
would expect |
D． |
expect |
It is not a problem ______ we can win the battle；it's just a matter of time．（ ）
| A． |
whether |
B． |
why |
C． |
when |
D． |
where |
Building such a bridge over the bay was ______，but the local government made it within two years．（ ）
| A． |
a wet blanket |
B． |
a piece of cake |
| C． |
a dark horse |
D． |
a hard nut to crack |