ANS:B - decreases

The occurrence of "case hardening" during drying of a high moisture solid cake typically decreases the drying rate. Case hardening happens when the outer layer of the solid cake forms a hardened crust due to rapid moisture removal, while moisture remains trapped inside. This hardened crust acts as a barrier, hindering further moisture diffusion from the interior of the cake to the surface. As a result, the drying rate slows down because it becomes increasingly difficult for moisture to escape from the solid matrix. Therefore, the correct answer is: "decreases".