--How did she get infected?
--She the virus without any protection.
A. exposed to
B. had been exposed to
C. had exposed to
D. was exposed to
网友回答
A. exposed to
B. had been exposed to
C. had exposed to
(答案→)D. was exposed to
解析：考查时态。句意：--她是怎样被感染的？--她暴露于病毒中而未采取任何保护措施。be exposed to sth暴露于......，是固定搭配。排除A、C；这里没有明显的过去的动作，不能用过去完成时；叙述过去发生的事情，用一般过去时。故选D。