If an air traffic controller is describing the speed of an airplane as well as the direction in which it should begin its decent, then the air traffic controller is describing the airplane's

a. magnitude.

b. velocity.

c. speed.

d. acceleration.

I think the correct answer from the choices listed above is option B. The air traffic controller is describing the airplane's velocity. Velocity is a physical vector quantity; both magnitude and direction are needed to define it. Hope this answers the question. Have a nice day.