It was supposed to be "Rabbits eating vegetables." But the latter word wasn't familiar to my low level elementary students, whereas they all knew the word "basketball." So when we recited the little dialog in chapter 9, that's how it came out.
I tried to explain that rabbits don't eat basketballs, but rather, vegetables. And I drew a picture on the blackboard, to explain why. I don't have that picture – a student who found it disturbing erased it too quickly. But I have a reproduction that I drew just now – see picture at right.