|Spanish interrogative pronouns are those used in interrogative sentences, as you may already know. Their English equivalents are "who", "what", "where", etc.|
Here's the list, with some examples:
¿Qué hora es?
¿Dónde está el perro?
¿Cuándo vas a hablar con mamá?
¿Por qué...? (Why...?)
¿Por qué estudias español?
¿Quién es esa chica?
Notice all these pronouns take the accent. This is the first point you have to learn. All interrogative pronouns must always take the accent.
So, whenever we ask a question, the corresponding interrogative pronoun needs the accent.