What characterizes negative longitudinal stability?

Negative longitudinal stability occurs when the center of pressure is located forward of the center of gravity. In this situation, any perturbation that causes the aircraft to pitch down will result in the center of pressure being further forward than the center of gravity. This causes an increase in the nose-down moment, making the aircraft inherently unstable. When the center of pressure is ahead of the center of gravity, the aircraft tends to move in a direction that increases this instability, as the aerodynamic forces act to pitch the nose down further rather than to restore the aircraft to level flight.

The other choices describe scenarios that do not lead to negative longitudinal stability. For instance, having the center of gravity behind the center of pressure would actually contribute to positive stability, as any nose-down pitch would result in a restoring moment that could help bring the aircraft back to level flight. Even distribution of weight across the wings refers to balance and does not directly correlate with stability in the longitudinal axis. An aircraft with high aspect ratio wings is generally associated with better aerodynamic efficiency and handling characteristics but is not inherently indicative of longitudinal stability itself.