What is typically the base spirit in a whiskey sour?

In a whiskey sour, the base spirit is whiskey, which is why the correct answer is whiskey. This classic cocktail includes a combination of whiskey, lemon juice, and a sweetener such as simple syrup. The use of whiskey gives the drink its distinctive flavor profile, character, and depth.

The choice of whiskey is essential as it influences the overall taste of the cocktail – whether it's bourbon, rye, or another style can create different nuances. The tartness of the lemon juice balances the rich, robust notes of the whiskey, making this drink a well-rounded and popular option in the cocktail repertoire. Other spirits, like vodka, gin, or rum, are not traditionally used in this specific cocktail, as they would fundamentally change the drink’s identity and flavor.