Chang’e2 did many experiments, ______ I think are of much help for knowing space.
----You forgot your keys when you left home in the morning. ----Good heavens, ___________.
Was it not until you began to work ______ how much time you had wasted?
A man does not know the difficulty of anything_________ he does it personally.
I caught the last bus from town, but Harry came home___________ that night.
Mrs. Green wants to buy that kind of cloth because she___________ that the cloth__________ very well.