a. The doctor had a lot to think   ( )before he really knew what was wrong with the man.

b. Your parents both work, so who looked   ( )you when you were young?

c. All my friends are on holiday and there is nobody to spend time   ( )or to talk   ( ).

d. I went to the cinema to see that film you talked   ( ), but it was boring.

e. I have never eaten sushi. What is it   ( )?

f. This is the third time I have been  ( ) Beijing. I really find it interesting.