Who was it?哪位？ /谁呀?
I heard the phone ring. Who was it?
我听见电话响了，是谁呀？
It was a salesman from an insurance company.
保险公司的推销员。

Who is this?哪位？
Hi，it’s Tracey. Who is this?
你好，我是特雷西，你是谁？
It’s Steve. Don’t you recognize my voice?
我是史蒂夫，听不出我的声音吗？