The correct answer is C) freeing ports. Freeing ports are openings or holes in the bulwark (the wall around the edge of a ship's deck) that allow water on the deck to drain into the sea. This helps prevent water from accumulating on the deck, which could be a safety hazard and make the ship less stable. The regulations for merchant vessels require the installation of freeing ports to ensure adequate drainage of water from the deck. The other answer choices are incorrect. Doggers are devices used to secure the hatches, swash ports are openings to allow water flow between compartments, and fidleys are ventilation openings, none of which specifically refer to the drainage of water from the deck.