Final answer:
The minimum following distance between two towing vehicles depends on several factors, including vehicle speed and cannot be determined from the provided options without additional context.
Step-by-step explanation:
Minimum Following Distance Between Towed Vehicles
Regarding the scenario where a truck is towing a vehicle, and another vehicle is towing a vehicle, the question of what is the minimum safe following distance one of these vehicles should maintain from the other does not have a universal answer provided in the context of the question. The minimum distance to follow another vehicle can vary based on a multitude of factors, including but not limited to the speed of the vehicles, road conditions, weather conditions, and local traffic regulations. Typically, many traffic safety organizations recommend a minimum three-second rule, which does not translate to a specific distance measured in feet without knowing the speed of the vehicle. Therefore, the correct answer among the provided options would be: d) It depends on the speed of the vehicles.