Oranges, lemons, watermelons, and tomatoes are berries.

The botanical definition of a berry is a fleshy fruit produced from a single ovary. Under this definition, tomatoes are berries, but oranges and lemons are modified berries called hesperidia, and watermelons are a type of berry called pepo. However, these are specialized subcategories. The statement oversimplifies by calling them all simply 'berries' without qualification.