Look at these details from a paragraph about the same topic:

Question

Watermelons are usually round, but they can also be square or heart-shaped.
Watermelons can be as small as oranges or as large as pumpkins.
The insides of watermelons can be red, white, yellow, or orange.
Choose the main, or central, idea that ties all the details together.

Answer 1

The central idea that ties all the details about watermelons together is that watermelons come in a variety of shapes, sizes, and internal colors.