题目解析:
根据题干中关键词”nonvolcanic islands” 定位到“As the continent broke up, the pieces moving apart left bits behind, explaining the presence of nonvolcanic islands and island chains, according to Wegener.”可知非火山岛的出现是为了表明大陆曾经是一个整体,后来 broke up 了,对应 B 选项。A,C 不在定位范围,D 未提及。