Which condition describes a restrictive soil layer?

The correct choice describes a restrictive soil layer as one that impedes the movement of water and air, as well as plant growth. This is significant because restrictive layers can create barriers that limit the ability of roots to grow and access necessary resources, such as water and nutrients.

In contrast, a layer that allows free movement of water and air would not be considered restrictive, as it promotes healthy soil conditions. Similarly, a layer that facilitates root growth indicates a supportive environment for plant development and would also not meet the criteria of a restrictive layer. Lastly, while a layer composed entirely of organic matter might have its own characteristics, it does not inherently indicate a restriction on water movement or root growth. Therefore, the defining feature of a restrictive soil layer lies in its ability to obstruct these critical processes, making it a barrier to optimal soil health and plant growth.