i,--------- am you friend,will try my best to help you out.

i,_________ am you friend,will try my best to help you out.
a.which is
b.which are
c.who is
d.who am
这是定语从句吗,如果是,who可以引导非限制性定语从句吗?
多了个am，不好意思
少个字母‘r’