Final answer:
The correct answer is option (b). During the day, there is low pressure on the slopes and high pressure in the valley, which causes valley breezes.
Step-by-step explanation:
The correct statement about valley breezes is B. During the day, there is low pressure on the slopes and high pressure in the valley. This occurs because, during the daytime, the slopes of the valley heat up more quickly than the air at the bottom of the valley, creating a region of lower pressure.
The cooler, denser air in the valley creates a region of higher pressure. As a result, the air moves from the high-pressure area in the valley towards the low-pressure area on the mountain slopes, forming a valley breeze.
Similar to sea breezes, which are caused by differential heating between land and water, valley breezes are a result of the differential heating between the valley floor and the surrounding slopes. The specific heat capacities of substances and the concept of convection and pressure differences in the atmosphere are essential for understanding these weather phenomena.