The Flight Deck Door must be opened with which of the following precautions?

The correct precaution to take when opening the Flight Deck Door is ensuring that the flight attendant's jumpseat is stowed. This is essential for several reasons: it helps to maintain a clear and safe passage for the crew to access the flight deck, and it prevents any potential obstruction that could impede emergency procedures or safety protocols. Stowing the jumpseat allows the flight attendant to move freely and quickly in case they need to respond to an unusual situation or threat.

While other options may have their significance in overall safety and protocol, they do not specifically address the critical aspect of preparing the cabin for the safe opening of the Flight Deck Door. For instance, ensuring crew members are seated is important for safety during taxi and landing but does not specifically relate to the danger associated with the door. Similarly, having passengers quiet or a secure cabin are relevant for general atmosphere and order on the flight, but they do not directly impact the safety measures necessary for opening the flight deck access.

Thus, ensuring the jumpseat is stowed is the most pertinent precaution to take when accessing the flight deck.