During an emergency evacuation, what step should be taken regarding the parking brake?

Setting the parking brake during an emergency evacuation is crucial because it ensures that the aircraft remains stationary, preventing any unintended movement. This action helps to maintain control of the aircraft's position on the ground, especially in chaotic situations where the crew and passengers may be evacuating quickly. By securing the aircraft, it mitigates risks associated with inadvertent rolling, which could pose a hazard to those evacuating the aircraft or emergency responders.

Releasing the parking brake may lead to the aircraft moving, potentially creating additional dangers. Checking fuel levels or donning oxygen masks, while important in certain contexts, are not directly related to the immediate needs of maintaining safety and control during an evacuation. The correct action prioritizes the safety of everyone involved during a critical situation.