Answer: During the day, valley air heats rapidly and rises upslope. At night, mountain air cools quicker and moves downslope into the valley.
Explanation:
The correct statement about Mountain-Valley breezes is that during the day, the valley air heats rapidly and then rises upslope while at night, mountain air cools quicker and then moves downslope into the valley.
During the day, when the valley floor warms, it should be noted that the warm air will then rise up to the slopes of the mountains that are around its surrounding which brings about a valley breeze.
Then during the night, the denser cool air will then slides downward the slopes and then settle in the valley which then gives the mountain breeze.
Therefore, the correct option is A.