Which of the following represents a decrease in velocity?

A decrease in velocity is represented by negative acceleration. Negative acceleration, also known as deceleration, occurs when an object is slowing down. This means that the object's speed is decreasing over time, which leads to a reduction in its overall velocity.

When an object experiences negative acceleration, it indicates that the direction of the object's velocity is opposite to that of its acceleration. For example, if a car is moving forward and starts to slow down, it is experiencing negative acceleration, marking a decrease in its velocity.

In contrast, positive acceleration indicates an increase in velocity, while zero acceleration means that the object's speed is constant and does not change. Constant velocity means that there is no change in speed or direction, therefore not signifying any decrease in velocity.