Why is "Quando tu bevi il vino?" incorrect? Does using a question word like "quando" preclude using the pronoun?
I think it's because the pronoun should follow the verb when it's a question (so in English it would be "when drink you wine." I THINK, but I'm no expert.
I'm pretty sure that it's because the "bevi" verb form already indicates the subject; ie, "bevi il vino" means "you drink wine." So including "tu" is probably like saying "When do you you drink wine?"