human
Question: An air mass in a valley travels up a mountainside. What causes the movement of this air?

Choices:
A) tidal pull of the moon's gravity
B) evaporation of water from soil in the valley
C) warming by solar energy re-radiated from the ground
D) cooling effect of ice crystals in the air over the mountain
gpt
The correct answer is 2: warming by solar energy re-radiated from the ground.