happen to be doing

happen to be doing happen to do和happen to be doing 的区别?顺便分别解释下.我问的是happen to be doing 不是happen to doing~ happen to 未发生 happen to be doing 正在发生 happen to hhappen to 未发生happen to be doing 正在发生happen to have done 已发生是这样区别的吗?老师说是.有点不确定 happen to do or happen doing? 有没有happen to doing? happen to do和happen to be doing有什么区别?区别是?HAPPEN TO BE DOING加的是进行时是吗?那是不是不能加结束性动词（短暂动词）了 whatever happen to doing啥意思 happen to dohappen to be doing happen to have done翻译下,还有没有其他的词语也能这样用,这种用法叫什么名字,再多举些例子 英语happen句型造句用1、sth.happen(s) to sb.2、It happen(s) that 3、sb.happens to be doing/to do三种句型各造些句子＜特别是第三个to be doing那个＞关于第三个的doing句型是重点..... be close to doing. be reduced to doing pretend to be doing there happened to be 还是there happen to be把happen换成appear呢? some groups of people just happen to be fatter than others.happen to be什么结构 问个关于happen的用法的问题.happen.不是happen to do sth.那么 碰巧去做,碰巧正做,和碰巧已做.是不是分别是happen to do,happen to doing,happen to have been? to be doing 和 doing的区别 be important to doing 对吗 Be conductive to doing 是什么意思?