I think it is OK to say "some people believe X, some believe X.... I don't know which is right" Allowing them to accept that they don't have to have "THE" right answer... and that what people believe are "theories" for lack of a better word... will give them the power to use their own discernment and mind to calculate and draw their own conclusions. I don't think you have to give them "the right" answer... you know what I mean?
My motto is to be honest, and give a lot of information- while it may be annoying to have other beliefs pushed on your child, it is a great exercise of tolerance for them.