The group of research workers are said to to the dangerous nuclear radiation while they carried out their rescue task.
A. be exposed
B. have been exposed
C. exposed
D. be exposing
网友回答
A. be exposed
(答案→)B. have been exposed
C. exposed
D. be exposing
解析： 考查非谓语动词。are said to do…据说……，所以排除C；且动词expose和逻辑主语The group of research workers是动宾关系，所以要用不定式的被动形式，排除D；expose这一动作发生在主句谓语动词are said之前，所以要用不定式的完成被动式。所以选B。