The correct answer is D) provides openings through the bulwark for mooring lines. A chock is a deck fitting that provides an opening or gap in the bulwark to allow mooring lines to pass through. This is necessary to secure the vessel to a dock or pier. The chock prevents the mooring line from becoming pinched or damaged as it passes over the bulwark. The other answer choices are incorrect. A chock does not permit jettisoning of deck cargo (A), it is not used to shackle gear to the deck (B), and it does not prevent stress concentration in the bulwark (C).