谁【shéi】

shéi谁 asks "who", and it stands in the slot the answer would fill.

There is no separate "whom": 谁 covers both, because it sits wherever the person belongs.

Two pronunciations

谁 is read shéi or shuí. shéi is what you hear in conversation; shuí belongs to careful reading and formal speech. Same character, same meaning.

After a preposition

With a preposition, 谁 stays with it in front of the verb.

shéi谁de的 asks "whose".

谁 as "everyone" and "no one"

With 都 or 也 after it, 谁 stops asking and means "everybody" or, under negation, "nobody".

Common mistake

谁 already makes the sentence a question, so it takes no 吗.

• × 谁是你的老师吗？ → 谁是你的老师？