who am 我是谁?(问句)
Pls guess who I am 请猜猜我是谁 (这个已经不是问句了)
一些其他的例子:
I don't know who he is 我不知道他是谁 (陈述句)
who is he?他是谁?(问句)
从语法上分析,I don't know who he is.
I (主语) don't (助动词),know (动词),who he is (名词子句,作宾语).