When I got into the room, Green was talking _________ the phone.
More and more trees were cut down. _____, many animals are dying out.
We should often keep _____ touch with each other, because we are good friends.
—What do you think this coat is made _____?—Wool. It’s used for _____.
—Do you know _____?—Sorry, I don’t know.
_____ the morning of December 1st, 2006, the 15th Asia Games _____ in Doha(多哈).