Final answer:
Acceleration is the rate at which velocity changes. The magnitude of the acceleration corresponds to the speed of the particle.
Step-by-step explanation:
Acceleration is the rate at which velocity changes. It is a vector quantity that has both magnitude and direction. The magnitude of acceleration represents the rate at which the velocity of a particle is changing, regardless of its direction. Therefore, the magnitude of the acceleration of the particle corresponds to option A, which is the speed of the particle.