The government of the United States began at once to investigate the case a lot of students were killed.
A. that
B. when
C. where
D. why
网友回答
A. that
B. when
(答案→)C. where
D. why
解析：考查定语从句，先行词是case，定语从句中缺少地点状语，用where引导定语从句，句意：美国政府立刻开始调查这个很多学生死亡的案件。选C。