Which of the following is commonly used as a garnish in many cocktails?

The correct choice encompasses all the options provided, highlighting that various garnishes can enhance a cocktail's visual appeal, flavor, and aroma. Mint leaves are frequently used in cocktails such as mojitos and juleps, where they impart a refreshing scent and taste. Cherries are classic garnishes for drinks like the Manhattan or the Old Fashioned, adding a pop of color and a touch of sweetness. An orange slice is often found in cocktails like the Screwdriver or as a decorative element for drinks served on the rocks, providing both aesthetic value and a hint of citrus flavor.

By understanding that all these garnishes play integral roles in cocktail presentation and enjoyment, it becomes clear why the correct answer is the inclusive option of all the above. Each garnish has its unique contribution, making them commonly used in cocktail preparation.