I think shree5 is right. I once questioned the authority on a topic of my high school english teacher, well i got a good reprimand for my troubles. the teacher took such an offence that she wan not satisfied by outting me down, she had to go ahead and make an example of me on other classes too..... i stopped asking questions after that. Another factor that stops me asking question is the fear of appearing stupid in front of the class.... hehe i guess that happens to a lot of other people too......