The correct answer is B. Temperature.
Temperature is a measure of the average kinetic energy of the particles in a substance. The higher the temperature, the faster the particles are moving. This is why hot air rises and cold air sinks.
Pressure is a measure of the force exerted by a substance per unit area. It is caused by the collisions of the particles in the substance with the walls of the container.
Density is a measure of the mass of a substance per unit volume. It is determined by the number of particles in the substance and the size of the particles.
Heat is a form of energy that is transferred from one object to another due to a difference in temperature. It is caused by the movement of particles in the substance.
In conclusion, temperature is the only option that provides a measure of the average speed of air molecules.