What is the primary component of a single shot of espresso?

The primary component of a single shot of espresso is indeed 30 ml of coffee. This measurement refers to the volume of brewed espresso extracted from finely ground coffee beans, typically using espresso machines.

Espresso is characterized by its concentrated flavor and creamy texture, which is achieved by forcing hot water through the coffee grounds at high pressure. The 30 ml measurement represents the standard serving size for a single shot, which is rich in flavor and provides the foundation for many coffee drinks.

The other options involve different components not representative of an espresso shot; for instance, 60 ml of water is often used to brew coffee, but that is not the serving size for espresso itself. Similarly, 30 ml of milk would not be considered a component of espresso, as it represents a different drink altogether. Lastly, 200 ml of water is significantly more than what is used in a single espresso shot and would dilute the coffee instead of providing the rich flavor profile associated with espresso.