My dad asks stupid questions and when I answer, he thinks I am trying to be a smart ass, what should I say to him?

I have that same problem. Normally I try to answer calmly and tell him that the question he asked is a question that he could have answered himself. If he still gets mad, just say that all you did was answer the question he asked you. After that, I normally go to my room or somewhere I can be away from everyone and try to think about what I said, and if he had a right to get mad, or if he didn't. I try to go to someone I trust after I take a moment to breath and calm down and tell them what happened and ask them what they think.