The correct answer is D. Parallel to stratification may or may not be greater than that perpendicular to stratification.
The coefficient of permeability is a measure of how easily a fluid can flow through a porous medium. In the case of natural deposits, the permeability is often anisotropic, meaning that it is different in different directions. This is because the deposits are often layered, with each layer having different properties. The permeability is typically greater in the direction parallel to the layers than in the direction perpendicular to the layers. However, this is not always the case, and the permeability can vary depending on the specific properties of the deposit.
Option A is incorrect because the permeability is not always greater parallel to stratification. Option B is incorrect because the permeability is not always less parallel to stratification. Option C is incorrect because the permeability is not always the same in both directions.