-Why didn't you tell me the truth? -Where DO you usually go on vacation? -Haven't you done the homework yet? -What HAPPENED at the meeting yesterday? -Who is Carlos going out with? -How FAR is it to the station? -How many people CAME to your party? -Whose jacket did you borrow for the wedding? -Why IS Mariana driving your car? -Excuse me. Can you tell me where the restrooms ARE ? -How LONG have you been studying Italian FOR ?

For number three its clearer to say: Why haven't you done the homework yet?

You can also the fourth sentence as it is. You usually hear this question when you want clarity about something that happened. Ex) dialogue between two co-workers: Frank: hey, Brian, how's it going? Brian: good Frank, thanks for asking. Brian: and how is the family doing? Frank: great! Brian: I heard the boss went off on Samantha yesterday, basically made the poor girl cry. Frank: no, that is not what happened. Who told you that? Brian: it doesn't matter. Tell me then, what DID happen at the meeting yesterday. Again, in the above sentence you are just trying to get a clear picture, the truth. Also, in your ninth sentence, "Why Mariana is driving your car?" Keep in mind the S.V.O. (subject, verb, object) English sentence order. The sentence should read "Why is Mariana driving your car?" Lastly, the last sentence. "How much time have you been studying Italian?" The phrase "much time" is used in the present tense or in the past simple, e.g. "How much time do we have left?," "I asked my brother how much time was left in the game." Think of a movie, someone is lying on the operating table, dying. the doctor may say, "There is not much time left. He will die soon, so say your goodbyes." Hopefully this helps a little man. But great job, keep it up!