The flu is believed by viruses that like to reproduce in the cells inside the hu
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The flu is believed__________by viruses that like to reproduce in the cells inside the human nose and throat.?
A.causing?
B.being caused?
C.to be caused?
D.be have caused?
试题答案
C
本题考查非谓语动词。在英语中表示“据说／传／知道……”的句型是It is said/reported/known that somebody/something...＝Somebody/Something is said/reported/known to...；流感是被引起的，所以选Ｃ。