There a terrible accident then, three passengers were killed and twenty were injured as

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A. was occurred; which
B. was occurred; in which
C. occurred; which
(答案→)D. occurred; in which
解析：考查There be句型的变形和定语从句，There occurred…“发生了”，第二空填，in which引导定语从句，先行词是a terrible accident，定语从句中缺少地点状语，用where或in which。句意：那时发生了一场可怕的事故，其中三人死亡20人受伤。选D。