Which part adds moisture, flavor, and holds the sandwich together?

The correct choice is a spread, as it plays a crucial role in enhancing a sandwich. Spreads, like mayonnaise, mustard, or hummus, add moisture and flavor, which are essential for making the sandwich more enjoyable. They can also provide a contrast in texture and taste to the other ingredients, improving the overall eating experience. Additionally, spreads help to hold the sandwich components together, ensuring that fillings stay in place and do not fall out during consumption. This cohesive aspect of spreads is significant in both the presentation and functionality of the sandwich.

While sauces and fillings contribute to flavor and texture, spreads are specifically designed to serve this multiple purpose effectively. Bread serves as the structural base but does not add flavor and moisture in the same way that a spread does. Therefore, choosing spread highlights its distinctive role in assembling a balanced and satisfying sandwich.