A-A+
______ experiments in the lab it started to r
问题详情
______ experiments in the lab, it started to rain heavily.
A．While he was performing
B．While performing
C．To perform
D．Performing
参考答案
正确答案：A
解析：句意：他在实验室进行实验时，天下起了倾盆大雨。考查从句和非谓语动词用法。【B】【D】选项要求主句主语it和performing之间是主动关系，而事实上是被动关系。【C】动词不定式表将来，而该句的时间背景为过去。
