There are several determiners, pronouns, and adverbs which signal a question. Cual is a determiner and a pronoun meaning "which" or "what": * Tu veni de cual pais? — What country do you come from? * Cual fenetras es rompeda? — Which windows are broken? * Cual pinta tu prefere? — Which paint do you prefer? (uncountable) * Cual tu gusta? – Which do you like? * Cual tu prefere, la rojas o la verdes? — Which do you prefer, the reds or the greens? * Cual libro tu leje? = Tu leje cual libro? — Which book are you reading? You are reading which book?