Who must give permission to flood a magazine while inport?

The correct answer is that the Officer of the Deck must give permission to flood a magazine while inport. The Officer of the Deck is responsible for the safety and security of the ship while at sea or in port, and this includes overseeing all operations that could potentially impact these factors. Flooding a magazine is a critical operation that could affect ship stability and safety, so it's essential that it is managed by someone with the authority and knowledge to make such decisions. The Officer of the Deck coordinates the ship's operations, ensuring that all safety protocols are followed, particularly in sensitive areas like magazines that store munitions.

While the Captain, Executive Officer, and Chief Engineer have significant roles and responsibilities aboard the ship, the direct authority to grant permission for flooding, particularly while inport, is under the purview of the Officer of the Deck. This ensures that the action is taken under proper supervision and with regard for overall ship safety and readiness.