He was walking along the sands _______ he saw a big foot-print in the sand .
A. while            B. when              D. as           D. after

You’d better come back earlier _______ it is getting colder.

He always talks _______ he had been to outer space.

Persist to the end , _______ you are the only one left.

We’ll carry the work through , cost _______ it may .

_______ you have got used to it , you’ll like it .

I paid only 5 pounds for the book , _______I expected it would cost.

_______I know , the computer can never take the place of the human brain.

______ did it , I didn’t.

I sent the letter early that morning _______ she got it that afternoon.