初中英语问题can you tell me ( )?A who is he B he is who C who's th

初中英语问题
can you tell me ( )?
A who is he B he is who C who's this D who he is
我想知道在can you tell me 后用什么句序?该选什么?
（不要只说答案,要详细一点哦＾－＾）
（ ）hard they are working!
what后用名词 how后用形容词和副词
从这个句子后面来看我觉得应该用what
但是hard是名词吗?
( ）hard they are working!
they are working,不是和What noise they are making 一样吗?
how的话不是 How clever a boy he is!
How lovely the baby is!
我实在不理解为什么答案是HOW啊~~
哪位高手指点一下,拜托了^-^
我太笨了- -|||,哭~~