"你知道新校长是谁吗？"

Translation: Do you know who the new principal is?

[Hedwigechouette]

"do you know who the new headmaster is" was rejected but should be accepted

[Riven333]

Why is “吗” required here? “谁” is a question word so I thought it would be redundant to include 吗.

[NikolaiYourin]

This is how subordinate clauses are formed in Chinese:

• 新校长是谁？- Who is the new principal? (a simple question; note how this whole chunk will remain unchanged in the following sentences)

• 你知道新校长是谁。- You do know who the new principal is. (a declarative sentence - we need 吗 to turn it into a question)

• 你知道新校长是谁吗？- Do you know who the new principal is?

In a subordinate clause, 谁 loses its function as a question word and becomes a conjunction.

[limejuiceenjoyer]

My intuition is that it's because the 知道 turns it nominally into a yes-or-no question (do you know who they are, or not?) versus an open-ended question asking who the person actually is. I can't guarantee that this is accurate, though

[bourques100]

Tried "Do you know who's the new principal?" but it was rejected. Shouldn't it be correct?

[Dejo]

Avoid contractions like "who's" and you will save yourself headaches.

[StephanusG1]

In a subordinate clause the verb follows the subjects. The question inversion is in the first part of the sentence (do you know).

[DominicYoue]

Headteacher is another way of saying headmaster. Should be accepted.

[RajasDaithankar]

@Dominic - "College Principal", "Head instructor", "Teacher-in-chief", "Prime teacher"..... more ways of saying