When the audience heard the alarm, they all hurried to they thought was an emergency exit door.
A. what
B. which
C. where
D. who
网友回答
(答案→)A. what
B. which
C. where
D. who
解析：考查名词性从句。What连接宾语从句从句they thought was an emergency exit door并作从句的主语。 句意当观众听到警报声他们跑向紧急出口处。