The little girl felt sad ________ her pet dog died.A. why B. because of C. because
Mr Wang isn’t here , I think he __________ Shanghai .
--- Lily is ill in hospital .---Really ? I _____ know she was ill .
The task is so hard for e . I don’t know _______________.
Good books help us ___________ a whole new world to me .
There is no air _______ water on the moon .