The doctor did what he could_________ the dying man.
-----I have to go now. -----It is raining .Don’ t ______ until(直到) the rain stops.
I have a new ______ . I can put my money in it.
Water is very dangerous sometimes. So we must be careful _____ it.
In our city, _____ middle school students want to be a teacher in the future(将来) every year.
My brother is _____ his homework. He often _____ his homework at home.