To achieve a slower drop in the brake adjustment, which change should be made?

To achieve a slower drop in the brake adjustment, moving the BD resistor tap to the left is the correct adjustment because it alters the resistance in the braking system, thereby changing the brake control dynamics. Specifically, adjusting the resistor tap affects the current flowing through the brake system, which in turn influences the response time of the braking action. By moving the tap to the left, you increase the resistance, which results in a slower reduction in brake force. This allows for a more controlled and gradual drop in performance, helping to prevent sudden decreases in braking power that could lead to instability or loss of control in a vehicle.

Other modifications such as increasing the load weight or changing the brake fluid do not directly affect the rate of drop in the brake adjustment in terms of resistance timing. Similarly, shortening the spring length would generally increase the responsiveness of the brakes, leading to a quicker drop rather than a slower adjustment.