Final answer:
The student's question about the number of vehicles that can be towed by saddle mount cannot be answered definitively with the provided reference, which does not match the context of the question. The correct answer is option d. 2.
Step-by-step explanation:
The question is asking how many vehicles can be towed in combination using a saddle-mount towing method. Saddle-mount towing is a common method used for transporting multiple vehicles, where one vehicle tows another by mounting a portion of the towed vehicle's front wheels on a saddle or support at the rear of the towing vehicle.
The rules and regulations regarding the number of vehicles that can be legally towed in this manner can vary depending on the country or state's traffic regulations. However, based on the provided reference information, which seems to not match the context of the question, we cannot determine the correct answer. Therefore, I am unable to provide a definitive answer to this question about saddle-mount towing and the correct number of vehicles that can be towed.