Most whales must come up for air after several minutes, _______ a few can stay under water for an hour or more.
By far, there are many problems ________ to be solved.
I don't think _________ possible to master a foreign language without much memory work.
The patient was warned ________ oily food after the operation.
Susan, _____ university student from European, teacher me _____ art in he spare time.
—Catherine, I have cleaned the room for you. —Thanks, you __________it. I could manage it myself.