I wish to thank Professor Smith,without________help I would never have got this far.(2012·天津,7)
It's no use______ with him. You might as well ______ with a stone wall.
I couldn't understand ______ at the poor child.
We can't understand ______ a decision until it is too late.
Alien said that his trip was _______.
---- What do you think about English? ---- It's a difficult language _____.