What accident happened recently in Japan?这个特殊疑问句为什么没有助动词?是不是要改成 What accident did happened recently in Japan?还是有种语法

when did the accident happen What happen what happen a traffic accident ___(happen)to him there was a car accident yesterd. _____________________ 选择题选项为：a,What did Mr Hu happen? b,What did happen to Mr Hu?c,Mr Hu happened what? d,What happened to Mr Hu? What happen还是What is happen? 英语翻译What does the poster on the wall of the laboratory tell?What should you do if your teacher is not around when an accident happen? what will happen? What happen to What's happen? What will happen? what will happen then what will happen next? What happen is incorrect? what is happen what's happen What happen是什么意思 what happen是什么意思