—________is the apple? —It’s yellow.

—_____do you have for dinner?
—A big hamburger.

I don’t like running, _____I like swimming.

---_______do you send e-mails to your pen friend?  ------Once a month.

____ he was very tired, he didn't stop to have a rest.

-_______are you going for vacation?
-I am going to Canada.

Some people waste a lot of food___________ others don’t have enough to eat.

--- I feel nervous about the coming summer.
---- Me , too. Hot weather _____ makes people feel hot, ______ causes serious health problems.

A tourist will easily lose his way in Shanghai_____ he has a map or a guide.

His father has worked in this factory _____ he came here in 1980.
A. since        B.  for        C.  when