to be polite, always use "please" and "thank you" and speak with confidence.
also, its very strange that they do not give a response to your questions. these are your superiors or co-workers?
if this strange behavior (by THEM) continues, I would simply ask them what the problem is. Perhaps say something like. "I'm sorry, but could you give me an answer to my question?" or "could you please tell me if I am being inappropriate with my questions, because I'd like an answer?"