Which goes where? （结构：主语+谓语动词+地点状语）

一个特殊疑问句，可以同时含两个或以上的疑问代词或疑问副词，而且做不同的成分：

Now which is which?
现在，哪个是哪个呢？
Who knows where?
谁知道去了哪里？
The twins are so alike I can't tell which is which.
这一对双胞胎长得一模一样，我分不清谁是谁。
《牛津词典》
Who knows what they look like?
谁知道他们长什么样子呢？
Who knows what changes tomorrow may bring?
谁知道将来会有什么变化？
《牛津词典》