The correct answer is: A. First
Motor vehicles in closed wagons shall be attached in the first position from the engine on a goods train. This is because the first position is the safest position for the motor vehicle, as it is less likely to be involved in a collision. Additionally, the first position is the most convenient position for loading and unloading the motor vehicle.
The second position is not a safe position for the motor vehicle, as it is more likely to be involved in a collision. The third position is also not a safe position for the motor vehicle, as it is more likely to be involved in a collision.
Option D is incorrect, as it is not a valid option.