问题
选择题
While building a tunnel through the mountain, _______.
A．an underground lake was discovered
B．there was an underground lake discovered
C．a lake was discovered underground
D．the workers discovered an underground lake
答案
答案：D
主要测试一致关系。当分词作状语时，其逻辑主语就是句子主语。又因为现在分词表主动、进行，过去分词表被动、完成，所以只有选项D中的主语the workers才能发出building这个动作。