2038] While
building a tunnel through the mountain, _____.
[译文] 在大过山隧道的时候,工人们发现了这个地下湖。
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
[答案及简析]
D。 现在分词短语作状语,那么这个句子的主语必须能发出这个分词短语动作的人。