Which of the following is a key component of a hearty breakfast?

A croissant is considered a key component of a hearty breakfast because it is a rich, buttery pastry that adds both flavor and substance to a morning meal. Croissants are often enjoyed as part of a balanced breakfast due to their versatility; they can be served plain or filled with various ingredients, such as cheese or ham, which further enhances their heartiness.

In contrast, the other options, while they can be part of a breakfast, are generally lighter or less filling. For example, fruit salad provides vitamins and hydration but lacks the hearty qualities associated with more substantial dishes. Muffins can be filling, but they are often sweet and may not provide the savory satisfaction that one might seek in a hearty breakfast. Granola bars, while convenient, are typically more of a snack option rather than a central breakfast component. Their focus on convenience over substance limits their effectiveness as a hearty breakfast choice.