1 . —Are you guys ready for “The Campus Singers Competition”?
—Sure！Since we are young, try it, _____ we will regret!

A．and

B．but

C．or

D．then

2 . Relax yourself every day,________ you'll be too tired to get good grades.

A．and

B．or

C．for

D．but

3 . —Was it there _______ you were away to see your friend off?
—I’m not sure . But when I got back, it was gone.

A．that

B．which

C．where

D．while

4 . Be quiet______you will wake the whole house!

A．or

B．and

C．so

D．but

5 . —I don’t care for baseball.
—How can you say you don’t like something       you’ve never even tried it!

A．till

B．after

C．unless

D．when

6 . Most whales must come up for air after several minutes, _______ a few can stay under water for an hour or more.

A．while

B．or

C．for

D．so

7 . He made a mistake，but he corrected the situation       it went worse．

A．until

B．when

C．before

D．as

8 . We all know it will be next June        we can really have a rest.

A．when	B．before
C．since	D．until

9 . I had been puzzled over the problem for over an hour without any result, ____ all at once the solution flashed across my mind.

A．while

B．when

C．then

D．as

10 . _______ he was the last man I wanted to see, I did all that I could to help him.

A．As

B．Now that

C．While

D．As though