Which of the following is a feature of TCAS II?

Answer: A — Traffic and resolution advisories.

The feature of TCAS II that is highlighted as correct relates to its capability to provide traffic advisories and resolution advisories. TCAS, or Traffic Alert and Collision Avoidance System, is an aircraft system designed to enhance safety in the sky by reducing the risk of mid-air collisions. Traffic advisories alert pilots to the presence of nearby aircraft that may pose a threat, while resolution advisories provide specific instructions on how to respond to avoid a potential conflict. For example, a resolution advisory might instruct a pilot to climb or descend to maintain safe separation from another aircraft. This proactive approach is a hallmark of TCAS II, distinguishing it from simpler systems that might only offer proximity warnings without guidance on how to act. In contrast, proximity warnings merely inform the pilot of nearby traffic but do not provide resolution advisories. Speed advisories focus on airspeed management rather than vertical separation, and TCAS II does not command maneuvers in all directions but rather advises specific vertical maneuvers to maintain safe distances. Thus, the ability to provide both traffic and resolution advisories is a critical safety feature unique to TCAS II.