When does pressure mechanism occurs ?

Question

$\begin{array}{1 1} (a)\; \text{when sediments are buried deep under the ground} \\ (b)\; \text{when sediments are above the ground } \\ (c)\; \text{when sediments are just few feet below the ground level} \\ (d)\; \text{when sediments are formed as a layer above the ground level} \end{array}$