who’s that?回答到底用什么it’s that’s she’s 要准确的

1.敲门的时候
A（敲门）
B：who is that
A:It's Eva.(I'am Eva)
2.打电话的时候
A（打电话）
B：（接电话）who is that?
A:This is Eva
3.平通交谈,问“他/她/那是谁?”
A：who is that?
B :He/She is Eva.(That is my sister)
)