Final answer:
The most likely physical quantity being described in this question is velocity.
Step-by-step explanation:
The most likely physical quantity being described in this question is B) Velocity.
Velocity is a vector quantity that describes the rate at which an object changes its position in a specific direction. In this case, the outfielder is throwing a baseball to second base at a speed of 19.6 m/s, which corresponds to the magnitude of the velocity. The velocity also has a direction, which is determined by the direction of the throw.