What could be a potential issue when rejecting a takeoff after reaching V2?

Rejecting a takeoff after reaching V2 can lead to hot brakes from a sudden stop because V2 is the speed at which the aircraft can safely continue the takeoff in the event of an engine failure. At this point, the aircraft is typically at a significant speed and slowing it down quickly requires heavy braking to avoid overshooting the runway. This rapid deceleration generates a lot of heat in the brake system, which can lead to hot brakes.

In contrast, the other options present issues that are less relevant to the situation. Increased cabin pressure is not directly related to a takeoff rejection, as the aircraft's systems manage cabin pressure regardless of takeoff status. Decreased fuel efficiency is more of a concern during sustained flight operations rather than during a takeoff rejection. Lastly, passenger discomfort due to speed change can occur but is secondary to the mechanical consequences of hot brakes and does not address the immediate concerns for safety and aircraft performance.