题目
The flu is believed ________ by viruses that like to reproduce in the cells inside the human nose and throat. ( ) A. cause B. being caused C. to be caused D. to have caused
The flu is believed ________ by viruses that like to reproduce in the cells inside the human nose and throat. ( )
A. cause B. being caused C. to be caused D. to have caused
题目解答
答案
C
解析
本题考查动词不定式的被动形式在固定句型中的用法。关键点在于识别"believe"后的宾语补足语结构，以及被动语态的正确表达。需注意"be believed to be caused"这一固定搭配，表示“被普遍认为由……引起”。
句型结构分析
原句为被动句，主干为"The flu is believed ______ by viruses"。此处"believe"的宾语是"the flu"，空格处需填入动词不定式的被动形式作宾语补足语。
选项辨析
- A. cause：缺少不定式符号to，结构错误。
- B. being caused：使用现在分词的被动式，但"believe"后需接不定式，非进行时态。
- C. to be caused：正确形式，表示“被相信由……引起”。
- D. to have caused：表示已完成的动作，与语境中“普遍认为的成因”不符。