"Who took the last biscuit?" - subject question "Who did you take to the concert?" - object question (ie. You took somone... who was it?)

It sounds better who did take?

Technically, you could use both, but "who took" sounds more modern. Who did take is something you would find in an old English poem or book, and while you could use it without being incorrect, it is rarely used in English conversation today.

I don't have enough context to answer your question. A more correct form is Who took it? Or Did he/she/they take it?