The bridge was built in memory of the adventurer who was believed the valley.
A. to have been discovered
B. to discover
C. to have discovered
D. having been discovered
网友回答
A. to have been discovered
B. to discover
(答案→)C. to have discovered
D. having been discovered
解析：考察不定式用法。固定句式sb be believed to do sth某人被认为做某事。如果后面表示的事情是已经发生的，那么应该使用不定式的完成式to have done来表示。句意：这座桥梁被建设是为了纪念那位探险家，这个探险家被认为发现了这个峡谷。根据句意可知这位探险家发现这个峡谷是已经发生的事情，故使用不定式的完成式来表示。故C正确。