29.___ it be Li Ping who broke the glass?No.It __ be Wang Hai who
did it.分析为什么选D而不选B.30.When the old man was alive,he__ sit for hours at the door.为什么选A而不选C.32.I have decided to take the job and I ___ change my mind.A.must not B.can not C.won not D.may not 分析为什么选C而不选B.
29，a,could may b,can can c,may must d,can must