Aron's arm was caught under a 360-kilo rock that fell on him when he was climbing by himself in the mountains.这个句子的when从句是修饰哪个动词啊,是fell还是caught啊另外caught怎么理解啊
《高考英语备考1号·速效编》
《高考英语备考1号·写作编》
《高中英语晨读晚记》
《高中英语错题笔记》
《零起点考大学英语》