Final answer:
Backing is dangerous due to limited visibility and the risk of being struck by another vehicle.
Step-by-step explanation:
The key reason backing is so dangerous is because it gives you limited visibility, creating blind spots.
When backing up, you may not be able to see what is behind you, increasing the risk of collision with other vehicles, objects, or pedestrians.
Additionally, backing requires you to get out of your tractor, which increases the likelihood of being struck by another vehicle.
This is especially dangerous if you are in a busy or high-traffic area.
Therefore, the correct answer is option D: Both B and C. Backing can lead to limited visibility and the risk of being struck by another vehicle.