例句：

　　Who knows what changes tomorrow may bring?

　　誰(shuí)知道將來(lái)會(huì)有什么變化？

　　Who knows how to plant trees?

　　誰(shuí)知道如何種樹(shù)？

　　Who knows who is who?

　　誰(shuí)知道誰(shuí)是誰(shuí)？