问题补充：
The explorers failed to find the cave because it was not locatedthey had expected it to be.
A. which
B. that
C. where
D. what
答案：
A. which
B. that
(答案→)C. where
D. what
解析：考查从句辨析。句意：探险家们未能找到那个洞穴，因为它并不在原先预定好的位置。locate位于，根据locate可知，后面的从句表示的是一个地点，从句不缺成分，故用where引导从句。故选C。
