What is one of the three functions of the FACs?

Windshear detection is indeed one of the critical functions of the Flight Augmentation Computers (FACs) on the A320. These computers continuously monitor the aircraft's environment and performance parameters to identify potentially hazardous conditions, including windshear. Windshear refers to a sudden change in wind speed or direction and can pose significant risks during takeoff and landing phases. By detecting such conditions, the FACs can provide essential information to the pilots and can engage protective measures to help maintain safe flight.

While the other choices represent functions associated with various flight control systems, they do not specifically pertain to the FACs. Pitch protection and roll protection are related to functions provided by the flight control laws, ensuring the aircraft maintains safe operational limits during flight maneuvers. Abnormal attitude protection also falls under the domain of the flight control computer system, which works to help recover from unusual flight attitudes. The specific role of detecting windshear emphasizes the importance of situational awareness and automatic handling that the FACs provide, making it a critical aspect of flight safety operations.