What Is the Difference Between Speed and Velocity

What is the difference between speed and velocity?

A) Speed is the magnitude of velocity; velocity is a vector and has both magnitude and direction.
B) There is no difference.
C) Speed is the rate at which something moves, while velocity is the direction in which it moves.
D) Speed is used when describing motion in one dimension, while velocity is used when describing motion in two dimensions.
E) Speed is the rate at which velocity changes.