I tried to call you ________ I heard from him, but nobody answered the phone.

A. since

B. while

C. until

D. as soon as

Don't be afraid of asking for information ________ it is needed.

A. when

B. after

C. although

D. unless

You'll do much better ________ you're more careful with your spelling.

A. if

B. before

C. although

D. unless

She worked so quietly ________ no one knew she was there.

A. which

B. after

C. as

D. that

Her mother won't leave the TV set, ________ the children are waiting for their supper.

A. if

B. because

C. even though

D. as soon as

All of us will be happy ________ you can come with us.

A. while

B. if

C. but

D. or

Miss Zhao is very helpful, She often helps us ________ we are in trouble.

A. whether

B. although

C. whenever

D. however

He was so tired that he fell asleep ________ he went to bed.

A. as if

B. even though

C. ever since

D. as soon as

It's raining heavily outside. Don't leave ________ it stops.

A. when

B. since

C. while

D. until

Edison never gave up, ________ he failed many times.

A. and

B. though

C. or