“what had happened to the cameras by the time they reached the customers”的意思

What had happened?What had happened?What had happened? what is wrong had happened? I had no chance to explain what had happened的同义句 I didn't _______ explain what had what happened what had happened 有什么区别呢 I didn’t know what had happened to him 有语法错误吗 What had she happened?改为宾语从句 He d____ exacxtly what had happened. WHAT HAD HAPPENED这是什么形式 I asked him what had happened 为什么要用had happened 而不直接用happened I still don't know what ( ) while I was away from home.A.had happened B.happened选哪个?另一个为什么不选? 9.HE STILL DOESN'T KNOW WHAT __WHILE HE WAS AWAY FROM HOME.A:WOULD HAPPEN B:HAPPENED C:HAD HAPPENED D:HAPPENS I didn`t know __________ because it was dark.A)what`s happenedB)what was happenedC)what had happenedD)happened what选什么?为什么? He can't m- what happened yesterday. what happened t -----the real Alice Not only my husband but also I enjoy watching TVI--------- --------- ----------my husband enjoy watching TVI didn‘t know what had happened until you told meIt----------- -------------you told me that I knew what had happened What if something had happened to you?What if I couldn't get to you?What would I have done without 求翻译/ what happened to 和 what had happened to的区别是什么? What happened和What had happened意思 区别?使用的区别,在什么情况下使用?