Gravel clay. a. less permeable b. less porous c. more permeable

Option C, More Permeable

Explanation:

Gravels are more permeable than the clay. This is so because the gravel particles are large in size and therefore the inter particle space in gravel is large which allows more water (or any other fluid) to flow through it while in case of clay, the particles are very fine and minute due to which the inter particle space between the clay particles is very very small which allows reduced flow volume through the clay particle as compared to the gravel particles.