In a situation where it is impractical for a vessel to show towing lights while assisting a distressed vessel, what action is permissible?

Answer: D — Need not show towing lights

In scenarios where a vessel is assisting a distressed craft, if displaying towing lights is impractical, the regulations permit that the assisting vessel need not show those specific towing lights. This flexibility in the rules acknowledges that safety and practicality may take precedence in urgent situations, allowing for a more effective response when dealing with emergencies at sea. The lighting requirements can sometimes hinder the vessel's ability to operate safely, hence the allowance not to display towing lights under these circumstances. The other options are not aligned with the established navigation rules. For instance, showing all navigation lights would not be necessary since specific lighting conventions apply when in a towing scenario. Similarly, anchor lights are meant to indicate a vessel at rest, which is not applicable if the vessel is actively engaged in assisting another vessel. Lastly, stating that no lights should be shown at all contradicts the fundamental rules regarding visibility on the water, as vessels are generally required to display appropriate lights for safety and identification purposes.