some of the students saw this accident happen yesterday.happen为什么不用过去时happened
问题描述：
some of the students saw this accident happen yesterday.happen为什么不用过去时happened
答
see sth. do
答
see后面接动词原形
答
因为这是see sth do sth的结构.和整句时态无关.
还有see sb doing/do sth的结构.
答
saw 已经用了过去时了，如果是1个句子的话，后面动词都用原形