What are the root vegetables in the summer veggie salad?

The reason why the option that includes parsnips, turnips, red potatoes, red onion, and carrots is the correct choice is that these vegetables are typically classified as root vegetables. Root vegetables are those that grow underground, and they are known for their dense and starchy nature, which can add both flavor and texture to dishes.

Parsnips and turnips, for example, are especially notable for their sweet, earthy flavors. Red potatoes and carrots also fit this category as they are commonly used in various salads and dishes for their versatility and ability to complement other ingredients well. Red onions, while not a root vegetable in the same sense, are often found in salads for their sharp flavor.

Root vegetables are generally harvested in late summer and fall, but depending on the climate and growing conditions, many can still be found fresh in summer salads, which aligns with the context of a summer veggie salad. Thus, the mixture provided in this response showcases a well-rounded selection of root vegetables suitable for such a salad.