Final answer:
The average velocity of air molecules in a room is subsonic, but effectively zero due to the random directions of particle movement. Option b
Step-by-step explanation:
The average velocity of air molecules in the room you are in is subsonic. While individual air molecules at room temperature travel at speeds comparable to a speeding bullet, they do not reach supersonic speeds. Supersonic velocity is faster than the speed of sound in air, which is approximately 343 m/s at room temperature.
However, the average velocity results from the random motion of the molecules in many different directions, which means when considering the movement of all molecules collectively, their average velocity becomes zero because their individual movements in random directions cancel each other out. Option b