Final answer:
Speed is a scalar that measures the rate of motion without direction, while velocity is a vector that measures both rate and direction of motion. The correct answer to the question is D.
Step-by-step explanation:
The difference between speed and velocity is that speed is a scalar quantity that measures how fast an object moves, which means it only includes magnitude (how much) and doesn't account for direction.
In contrast, velocity is a vector quantity that not only measures the speed but also includes the direction in which an object is moving. The correct answer to the question is D. Velocity measures an object's rate and direction of motion, while speed measures the rate only.