20.He ______ two hours for his friend to arrive.
A.wait B.have waited C.waiting D.waited
21.Detectives always ______ for clues.
A.search B.searches C.searching D.none of the above
22.If you ______ more time studying, you will improve.
A.spend B.spends C.spent D.are spending
23.I always ______ my homework after dinner.
A.do B.does C.is doing D.doing
24.I ______ to music.
A.listens B.listening C.listen D.none of the above