What should be the focus when backing as close as possible?

The focus when backing as close as possible should be on minimizing the distance from an object. This approach ensures that you maintain safety and precision during the maneuver. By concentrating on the proximity to the object, you can better judge your vehicle's position in relation to it, which is crucial for avoiding collisions and ensuring that clearance is adequate. You will also have the opportunity to utilize your mirrors effectively, as well as other reference points in your environment, to assist in guiding the vehicle safely.

The other options involve factors that, while relevant to overall driving and safety, do not directly address the core objective of backing close to an object. For instance, speeding through the maneuver increases the risk of accidents and decreases the driver's ability to respond to immediate hazards. Relying on just one mirror could limit visibility and awareness, amending the effectiveness of the approach, and adjusting seat height may enhance comfort or visibility but does not directly influence the specific focus required in this scenario. Focusing on minimizing distance directly aligns with the goal of practicing precision and safe vehicle control when reversing.