When the AO approves a rental car for the traveler's use at the TDY location, which of the following is not a valid use of that official rental car?

The option indicating travel to visit relatives on non-duty days is not a valid use of an official rental car approved for a traveler at a Temporary Duty (TDY) location because the vehicle is intended solely for official business that directly relates to the traveler's duties. When a rental car is authorized, it is primarily meant for activities that support official functions such as attending meetings, training events, or other work-related responsibilities.

Using the rental car for personal visits, such as going to see relatives, does not align with the purpose of the official travel authorization. Personal use of government resources is typically prohibited, ensuring that public funds are utilized strictly for official government activities. This principle underlines the importance of maintaining accountability and responsible use of government assets.