What safety precaution must cabin crew take when the flight deck door is opened prematurely?

When the flight deck door is opened prematurely, it is crucial for cabin crew to stay alert and remain seated. This safety precaution is important because the unexpected opening of the door can lead to various security and safety risks. By staying alert, crew members can respond to any potential threats or emergencies that may arise and ensure the safety of passengers. Remaining seated helps maintain a controlled environment and reduces the risk of injury or chaos during an uncertain situation.

The other options do not address the immediate need for awareness and vigilance in this scenario. Calling for assistance, while sometimes necessary, may not be the best action during the opening of the door when immediate focus is required. Continuing with normal duties fails to account for the potential hazards associated with the door being open. Closing the door quickly, while seemingly intuitive, may not be feasible if there are operational protocols that must first be addressed or if the situation calls for a different approach. Thus, the chosen option effectively prioritizes safety and preparedness for any developments that could arise from the door's premature opening.