Betty: Black hens are more clever than white ones， aren’t they?

Mum: How do you know?

Betty: Well， the black hens can lay white eggs， but the white hens can’t lay black ones.

Only Play on the Black Notes

Jack: Mum， can I play the piano?

Mum: Not till you’ve washed your hands. They are dirty.

Jack: Oh， Mum——I’ll only play on the black notes.