From time to time a crocodile has snatched someone he or she is even aware that the crocodile is there.
A. when
B. until
C. since
D. before
网友回答
A. when
B. until
C. since
(答案→)D. before
解析：考查时间状语从句。句意“有时候，在人们意识到有鳄鱼之前，鳄鱼会突然捉住他。”A“当”；B“直到”；C“自从”；D“在......之前”。故选D。