Which of the following is NOT an ingredient in a Cosmopolitan?

The Cosmopolitan cocktail is traditionally composed of vodka, triple sec, lime juice, and cranberry juice. Each of these ingredients contributes to the drink’s characteristic flavor profile. Vodka serves as the base spirit, while triple sec adds a sweet, orange flavor, and lime juice provides a tartness that balances the sweetness.

Amaretto, on the other hand, is a sweet, almond-flavored liqueur. It is not used in a Cosmopolitan and would change the drink's fundamental flavor profile significantly. Therefore, its absence from the traditional recipe designates it as the correct answer to this question.

Understanding the composition of popular cocktails is critical for bartenders, as it ensures they can create classic drinks properly and provide customers with the expected taste and quality.