---It's very kind of you to see me off,Mr Johnson. ---______.It's the least we could do.
If _____ carefully, the experiment will be successful.
He is a man of few words, and seldom speaks until _____ to.
There are five pairs, but I'm at a loss which _____ to buy.
He was not an actor, who often appeared on stage, _____ a writer, writing stories.
I don't know whether to stay in teaching or _____ another job.