Another quick question.
Is it possible to show a spayed bitch?
If not, why not?
How do they know?

Yes, you can show a spayed bitch if you inform the KC of the operation. In reality I would imagine that there are bitches out there showing who are spayed because, as you say, how do they tell. However, if you get caught, you can have any awards taken away from you and be fined by the KC. Also, there are people who say that spayed bitches shouldn't be shown because the point of showing is to get teh best dogs for breeding purposes.
Joan :)

In some breeds it can be easy to tell because the coat changes texture (i.e. a wire coat can become soft & wooly).