A) shorten the hawser or increase the tug's speed is the correct answer. Shortening the hawser or increasing the tug's speed will reduce the amount of catenary, which is the sag or curve in the towing line between the tug and the vessel being towed. Reducing the catenary helps maintain better control and maneuverability of the tow. The other options are incorrect because lengthening the hawser or reducing the tug's speed would increase the catenary, which is the opposite of what is needed to reduce it. Making a sharp turn or placing the tug in irons (pointing the bow into the wind) would not directly affect the amount of catenary in the towing line.