Which ingredient is considered the primary flavor in an Aperol Spritz?

In an Aperol Spritz, the primary flavor comes from Aperol, which is an orange aperitif that is both bitter and sweet. Its distinct flavor profile, characterized by notes of orange, rhubarb, and herbs, is what primarily defines the cocktail. While Prosecco, soda, and orange contribute to the overall taste and balance of the drink, Aperol is the key ingredient that gives the Spritz its signature taste. This is why it is central to the cocktail’s identity and flavor profile, making it the correct answer.