You can’t be ______ when you camp _____ an high altitude, where the air is thin.
—Mary, are you sure your aunt ___ back from America?—Yes. My mother ___ me. I am going to see her now.
—Did you enjoy yourself last weekend, Tom?—Yes, as you know, ______ birthday party went on in _____ most pleasant atmosphere.
—Tony said he could fix my bicycle, but I really doubt it.—_______. He’s very good at this sort of thing.
This article may be some advice about how to _________ oneself in society.
The environmental problems in China may worsen if __________ unsolved.