riddles

well ! i was looking over my brother's homework just then and he had to match some riddles. Heres some that are quite interesting =)

What goes oom oom?  -  A cow walking backwards.
When is a bus not a bus? - When it turns into a street.
How do you make a witch itch? - Take away the w. 
Why was the Egyptian child confused? - His daddy was a mummy
Who was the English captain who came to Australia and never got a bat? - Captain Cook