Cause的选择题
问题描述：
Cause的选择题
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
答
C, 这是 sth is believed to be done 的句型,意思是“据信.”,而流感是被病毒引起的,所以是被动语态.