That portion of the runway identified by the letter A may be used for...

The correct answer indicates that the portion of the runway identified by the letter A can be used for taxiing and takeoff. This is a crucial understanding for pilots because runways are designated for different operational uses, and recognizing these designations ensures safe and efficient aircraft movement.

When a segment of the runway is specified for both taxiing and takeoff, it typically exists to facilitate the aircraft's transition from taxiing to the actual takeoff phase. This means that pilots can maneuver on this section of the runway while preparing for departure, adhering to air traffic control instructions and ensuring they are set for a safe takeoff.

Further clarity on this concept can be garnered by considering the other options. Landing usually pertains to the portion of the runway that is not designated for takeoff and taxiing. Similarly, takeoff only would imply that the area is strictly for initiating flight, which is more restrictive compared to the broader category of both taxiing and takeoff. Lastly, parking of aircraft occurs at designated parking areas, which are typically separate from runway operations to avoid congestion and maintain safety during other aircraft movements. Therefore, understanding the multi-functional use of runway portions maximizes airport efficiency and enhances safety practices.