A towing light, according to the Rules, is a __________.

Answer: C — yellow light

A towing light, as defined by the International Regulations for Preventing Collisions at Sea (COLREGs) and the associated rules applied in U.S. waters, is specifically identified as a yellow light. This signal is intended to indicate that a vessel is engaged in towing and is a crucial part of ensuring safe navigation on the water. The towing light is typically displayed on vessels that are towing other vessels or objects and is usually positioned at the stern of the towing vessel. Its color and visibility are important for other vessels to recognize the presence of the towing operation and to take the necessary precautions to avoid collisions. By using a yellow light, it sets a clear standard for identification of the towing vessel under various lighting conditions. In summary, recognizing that the towing light is a yellow light is essential for understanding how vessels communicate their navigational intentions to others, contributing to overall maritime safety.