What is the best way you think of ______ the environment?
We must______ using plastic bags in order to protect our earth..
Parents often ask us _____ water in our life.
E - mail is very popular today. People hardly post letters, _____?
Our country ______the sixth population census(人口普查) already.
— Many people eat_____ meat than they did before.—Yes, that’s why they’re getting fatter and fatter.