用所给词的适当形式填空

①—Where is Mr. Green?

—He (go) to Beijing on business.

②You mustn't swim in the lake. Look at the sign “No (swim). ”

③ After school, he always finishes (do) his homework first.

④ My sister (arrive) at the airport in two hours.

⑤ David is coming to visit us. I'm looking forward to (meet) him.