是谁在

who is …ing

→ 是
phrase Uncommon #10,412
who is …ing Used to ask who is performing an action; it is usually followed by a verb.
CH: 是谁在敲门?
EN: Who is knocking?

是谁在吹笛子

Who is playing the flute?

— 大红灯笼高高挂 (1991)

是谁在操纵?

Who’s pulling the strings?

— 印度有嘻哈 (2019)

我们知道是谁在搞鬼

We know who's behind this.

— I Am What I Am 2 (2024)

是谁在敲门?

Who is knocking at the door?

— 瓦塞浦黑帮(上) (2012)

是谁在尖叫?

Who is screaming?

— 八部半 (1963)

是谁在付钱给你们?

Who's paying you?

是谁在开枪

Who is shooting?

— 巴克劳 (2019)

你知道是谁在卖它。

You know who's selling it.

不知是谁在敲门。

I wonder who's knocking at the door.