happened and happening

happened and happening happened,happening为什么? 用happen,happening,happened造句 英语-什么时候用happened,什么时候用happening something interesting happening/happen/happened/happens was happened,was happening,happen,happened,happening的用法及区别 1998 witnessed sth happening/happened ? 那种表达是正确的? What happened与What's happening的区别 what happened?和 what's happening?是不是意思差不多?, 为什么有what happened却没有what happening,而只能是what is happening,两个动 英语翻译A.happened to B.was happened toc.was happening D.happen what is happening.what happened.what has happened.what is up