Which action must be avoided to prevent a spin?

To prevent a spin, it is essential to avoid climbing with a high angle of attack. When the aircraft is at a high angle of attack, it is closer to the critical angle, where airflow over the wings can separate. If the aircraft stalls while at this high angle of attack, it can result in an uncontrolled yaw and roll, leading to a spin. Keeping a lower angle of attack during climbs helps maintain controlled flight, reducing the risk of stalling and potential spin entry.

In contrast, level flight with low throttle, turning without banking, and descending at a low speed can present their own risks but are not directly linked to the initiation of a spin in the same way that a high angle of attack during a climb is. Level flight at low throttle can lead to other issues like insufficient power but does not inherently create conditions favorable for a spin. Similarly, turning without banking is an ineffective maneuver, and while descending at low speeds can increase the risk of a stall, it is the high angle of attack during climbing that significantly heightens the risk of entering a spin situation.