there are always some traffic accidents happening easily when the_英语解答

there are always some traffic accidents happening easily when the road is ......
为什么用happening?

人气：300 ℃　时间：2019-08-19 19:38:57

解答

there be 句型+动词ing形式；be 是be动词,happen 是动词,不能同时存在两个动词,所以happen 采用现在分词形式