Which statement about the vadose zone is true?

• A. Its pore spaces can be filled with any fluid
• B. It lies below the water table
• C. It has no pore spaces
• D. It is always fully saturated with water

Answer: (A)

The vadose zone is the unsaturated region above the water table where pore spaces are not completely filled with water. In this zone, the pores contain a mix of air and fluids, and the specific fluid occupying the pores can vary with conditions and contaminants—water, air, vapors, or other fluids can all be present. That variability is what the statement about pore spaces being filled with any fluid is getting at: the zone is not permanently water-filled and is not limited to a single fluid.

Why the other ideas don’t fit: the vadose zone sits above the water table, so it is not the same as the saturated zone below it. It definitely has pore spaces, so it is not correct to say it has none. And it is not always fully saturated with water; by definition it is partially saturated, with air occupying part of the pore space.