when I came in he happened to open the doora tragic traffic accident happened to her huaband.It happen that he had a mobile phone similar to the one I lostit happen that 表示碰巧啊那么 如果把这个改下 sth happen to sb就是说把主语改成从句的话 是不是这样的 it happen to sb that ... 有这样的结构么 ？不知道好像没有吧 我没有见过啊