哪【nǎ】

哪 asks "which". Like 这 and 那 it needs a measure word before the noun.

It stays where the answer would stand

Chinese does not move a question word to the front. Ask about the object and 哪个 sits in the object slot; ask about the subject and it sits in the subject slot.

The sentence takes no 吗 – a question word already makes it a question. nǐ你yāo要nǎ ge哪个má吗 is wrong.

哪 and 那 differ only by tone

nǎ asks; nà points. The characters are near-identical and the third tone is the only thing separating them in speech.

Plural and set phrases

哪些 asks "which ones". 哪国人 asks nationality, and 哪儿 asks where.