--How did he get infected?
--She the viruses without any protection.
A. exposed to
B. had exposed to
C. was exposed to
D. had been exposed
网友回答
A. exposed to
B. had exposed to
(答案→)C. was exposed to
D. had been exposed
解析：试题分析：考查时态和语态。根据句意，表被动，排除A，B。根据上下文可知，是陈述过去的一个事实，故使用一般过去时。句意：——他是怎样感染的？——在没有任何保护的情况下面临病毒感染。