What does the presence of two masthead lights on a towing vessel indicate?

The presence of two masthead lights on a towing vessel indicates that the vessel is towing another ship. More specifically, the configuration of lights is used to signal the size of the tow. If the towing vessel has two masthead lights and is less than 50 meters long with a tow less than 200 meters, this configuration is indeed appropriate. According to the COLREGs, the two masthead lights serve as a clear visual cue to other vessels about the nature of the towing operation, helping to ensure safe navigation and reduce the risk of collisions.

The choice regarding the vessel being over 50 meters pertains to different lighting requirements, as larger vessels may have additional lights. The option indicating that it is less than 50 meters long with a tow of less than 200 meters aligns with the specified criteria for using two masthead lights. The other choices either misidentify the function of the lights or provide incorrect specifications that do not match established maritime signaling practices.