what has happened?为什么用HAS

what has happened?为什么用HAS what happened what has happened what has happened是什么意思 what has happened? 为什么用has,括号内不填单词可以吗?no matter what (has) happened to you what has happened 中为什么要用has 而不用have 是what has happened to还是what has happened at what has happened to you what happened /what has hanppend/what has been haapening No matter what ( )happened to you.用have还是has what happened ?和what has happened ?的区别 What has happened和What was happened区别