What is a risk associated with taller tires regarding vehicle metrics?

The option regarding fluctuating speedometer readings is considered correct because taller tires change the overall circumference of the wheel. When a tire's diameter increases, the distance the vehicle travels with each rotation of the tire also increases. This alteration means that the speedometer, which is calibrated based on stock tire sizes, will no longer reflect the accurate speed of the vehicle. As the vehicle moves, the speedometer may show a speed that is lower than the actual speed, leading to fluctuating and inaccurate readings as the vehicle's speed changes.

In contrast, the other options are less directly impacted by simply increasing tire height. Issues like incorrect fuel gauge readings or odometer tracking may arise due to other mechanical or electronic malfunctions rather than tire size. While less responsive braking could be a concern with larger tires due to increased weight and the effect on braking distance, it is not as direct an issue as the impact on speedometer readings caused by taller tires.