THE DIFFERENCE BETWEEN XXXVII

What's the difference between:

1. Summer and winter?
2. Ignorance and apathy?
3. The Prince of Wales and a tennis ball?
4. A well-dressed bicyclist and a poorly dressed unicyclist?

Answers:

1. In winter the bare limbs are on the trees.
2. I don't know and I don't care.
3. One is heir to the throne and the other is thrown (in)to the air.
4. Attire ( a tire)