—Tom , Don’t talk. _______ what you are doing.—Sorry, Mr. Li.
—Have you _____ had dumplings? —No, not _____.
The shoes were worn out, what’s more, they aren’t worth _____.
— What's the population ____ the U.S.A?— The U.S.A has ____ population of 297 million.
We should plant more trees on ____ sides of the street.
---What are you going to do next weekend?---I _____ yet. Do you have any good ideas?