The blind spot behind the bus could extend up to ____________ feet.

The blind spot behind a school bus can indeed extend significantly, and recognizing this is essential for ensuring safety when operating such a large vehicle. The correct answer indicates that this blind spot can extend up to 400 feet. This extensive area is primarily due to the size and length of school buses; large vehicles have larger blind spots compared to smaller passenger vehicles.

Understanding the dimensions of the blind spot helps drivers to be more cautious and vigilant, especially in situations where children might be boarding or alighting from the bus. Awareness of this blind spot is crucial to prevent accidents, as this area is not visible to the driver through regular mirrors. Thus, the figure presented in the correct answer underscores the importance of thorough checks before moving the bus.

While there are other options with longer distances, knowing that the blind spot can extend to 400 feet provides a clear and effective framework for bus drivers when assessing the safety of their maneuvers in relation to surrounding vehicles and pedestrians.