Which is the best explanation for a convection current in the atmosphere? Hot air expands and rises to the top of the atmosphere, while the cool air stays below it.

Hot air expands and rises, becoming cooler and denser, then falling again in a continuous process

Cold air expands and rises, becoming warmer and contracting, then falling again in a continuous cycle.

Cold light air rises in the atmosphere, while the warmer air stays near the ground.