Choose the underlined words or phrases that are not correct in standard written English:
31.Today, many serious childhood diseases can prevent by early
32.Could violence be controlling more effectively if the police carried guns?
33.Mika insists on asking questions that have already answered 
34.It's important to help people who has no home and money
35.At the airport. I was waiting for friends I hadn't been seen for a long time
36.I enjoyed the  songs which were singing by the band
37.A waterway is a river or stream which is used to carrying boats with goods or passengers
38.My parents are people I can always relied on for support and help
39.Water is a chemical compund that is consisted of oxygen and hydrogen
40.I'd like to tell you about several problems I have had for I came here