What feature uses an up arrow and down arrow to communicate altitude changes of targets?

The Traffic Alert and Collision Avoidance System (TCAS) is designed to enhance safety in the airspace by providing pilots with information about nearby aircraft, specifically their altitude and potential collision threats. The system employs an up arrow and down arrow to indicate whether these targets are climbing or descending relative to the aircraft's altitude. This visual cue helps pilots quickly assess the vertical movement of surrounding traffic, allowing for timely and informed decision-making regarding maneuvers to avoid potential midair collisions.

The other options serve different purposes. ADS-B (Automatic Dependent Surveillance–Broadcast) primarily provides situational awareness and information to other aircraft and air traffic control by broadcasting GPS position data but does not use arrows for altitude changes. The Flight Management System is focused on navigation, route planning, and optimizing flight paths rather than real-time traffic avoidance. The Terrain Awareness System enhances a pilot's awareness of terrain and obstacles but does not communicate altitude changes of other aircraft in the same way TCAS does.