--Look!Whyaretheresomanypeople?--Therearesomepolicemen....

問題詳情：

--Look! Why are there so many people?

--There are some policemen. I think there ________ a traffic accident.

A. must have    B. can have            C. is going to be              D. must be

【回答】

D 

知識點：情態動詞

題型：選擇題