Who did it is still a mystery,为何这句没连接词呢?

Who did it is still a mystery,为何这句没连接词呢? Who kills her is still a mystery. ? It is still a mystery for Everything is still a mystery,isn't it how you got me blind is still a mystery,I can it you out of 英语翻译How you got me blind is still a mystery ．Risking it all ___caused the accident is still a complete mystery. how you got me blind is still a mystery. 关于主语从句形式主语it引导的主语从句,连接词可以用if么?It is still a question whether how you got me blind is still a mystery是什么歌的歌词? How and when he got to the village is still a mystery.这句话对吗? 1.___caused the accident is still a complete mystery.用how为什么