We use "which" as a determiner to ask a question about a specific group of people or things:我们用限定词“which”问特定的一组人或物:
Which restaurant did you go to?
Which countries in South America have you visited? When we are asking a general question we use "what" as a determiner:用“what”问较为普遍的问题:
What films do you like?
What university did you go to?