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
步骤 1：分析句子结构
句子的主语是 "The flu"，谓语是 "is believed"，后面的部分是宾语从句。宾语从句的主语是 "viruses"，宾语从句的谓语是 "to be caused"，宾语从句的宾语是 "by viruses"。
步骤 2：确定动词形式
"believe" 后面跟动词不定式，即 "to be caused"，表示被动语态。"cause" 的被动语态是 "be caused"，因此选择 "to be caused"。
步骤 3：验证选项
A. cause - 主动语态，不符合题意。
B. being caused - 现在分词被动语态，不符合题意。
C. to be caused - 动词不定式被动语态，符合题意。
D. to have caused - 动词不定式完成时，不符合题意。
句子的主语是 "The flu"，谓语是 "is believed"，后面的部分是宾语从句。宾语从句的主语是 "viruses"，宾语从句的谓语是 "to be caused"，宾语从句的宾语是 "by viruses"。
步骤 2：确定动词形式
"believe" 后面跟动词不定式，即 "to be caused"，表示被动语态。"cause" 的被动语态是 "be caused"，因此选择 "to be caused"。
步骤 3：验证选项
A. cause - 主动语态，不符合题意。
B. being caused - 现在分词被动语态，不符合题意。
C. to be caused - 动词不定式被动语态，符合题意。
D. to have caused - 动词不定式完成时，不符合题意。