Which of the following is the best climb speed to achieve maximum altitude?

The most appropriate answer for achieving maximum altitude in the PA-28A is associated with the best climb speed, which is typically denoted as Vy (best rate of climb speed). This speed provides the best altitude gain over time. In many PA-28A models, this speed is often around 79 KIAS, which means this is the optimal speed to maintain during a climb when the goal is to reach the highest altitude in the least amount of time.

Understanding why this particular speed is effective has to do with the aircraft's performance characteristics outlined in the Pilot Operating Handbook (POH). At Vy, the aircraft retains the most efficient lift-to-drag ratio, enabling better climb performance. Maintaining this speed reduces the chances of stalling while also allowing for the most power available to be used for climbing, rather than excess airspeed which could lead to wasted energy.

Other speeds, while they may be higher or lower, would either not utilize the engine's power as efficiently or could lead to reduced climb performance, which is why they are less suitable for maximizing altitude gain.