The correct answer is D) securely fastened. Fittings used for towing must be securely fastened to the towed vessel. This is a fundamental requirement for safe towing operations. The fittings need to be able to withstand the forces and stresses of the towing process, and they must be properly secured to the vessel's structure to prevent failure or separation during the tow. The other answer choices are incorrect. While Coast Guard approval and knowledge of the maximum working loads are important considerations, the primary requirement is that the towing fittings be securely fastened to the towed vessel. The position of the fittings, whether at the bow or elsewhere, is not the critical factor.