单选题 The Chisos Mountains in Big Bend National Park in Texas were created by volcanic eruption that occurred______.

A、 the area in which dinosaurs roamed
B、 when dinosaurs roamed the area
C、 did dinosaurs roam the area
D、 dinosaurs roaming the area

【正确答案】 B

【答案解析】解析：occur是不及物动词，句子的成分已经完整，那么空白处要填的只能是状语．选项中只有B(时间状语when引导时间状语从句)符合状语结构的要求：A如果改为“in thearea which dinosaurs roamed”就对了；C是倒装句，排除；D选项没有状语从句引导词，不能直接用在occur后面。故本题答案为B。