Final answer:
The upper groundwater zone, called the vadose zone, consists of unsaturated soil. The saturated zone consists of soil where all the spaces between the soil particles are filled with water. The water table is the boundary between the unsaturated and saturated zones. The correct answer is b.
Step-by-step explanation:
The upper groundwater zone, called the vadose zone, consists of unsaturated soil. It is the zone between the land surface and the water table where the soil pores are not completely filled with water. This means that there is both air and water in the pore spaces of the soil. The saturated zone, on the other hand, consists of soil where all the spaces between the soil particles are filled with water. The water table is the boundary between the unsaturated and saturated zones. The correct answer is b.