The correct answer is D) provides an effective catenary and absorbs shock due to its weight. The chain bridle is used when towing astern because the weight of the chains creates an effective catenary (a curved shape) in the tow line, which helps to absorb the shock and strain on the towing vessel and the towed vessel during the towing operation. The catenary effect of the chain bridle prevents the tow from yawing or experiencing sudden jerks, which can be dangerous. The other options are incorrect because: A) a swivel is still necessary to prevent the tow from twisting; B) the ease of connection is not the primary reason for using a chain bridle; and C) while the chains do help prevent yawing, this is not the main reason for using a chain bridle.