While building a tunnel through the mountains, .A. an underground lake was discovered B. t

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A. an underground lake was discovered
B. there was an underground lake discovered
C. a lake was discovered underground
(答案→)D. the workers discovered an underground lake
解析：考查分词做状语的用法。当分词做状语的时候，分词的逻辑主语要是句子的主语，现在分词的逻辑主语是动作的发出者，过去分词的逻辑主语是动作的承受者。本题使用了现在分词building…做状语，那么building的逻辑主语即该动作的发出者（通常是人）就是后面句子的主语。ABC三项的主语都不是人，故D正确。