It is painful to walk bare footed on a road converted with pebbles because

Question

$\begin{array}{1 1} (a)\;\text{pebbles exert a large pressure on our foot } \\ (b)\; \text{pebbles exert very less pressure on our foot} \\ (c)\; \text{our body weight is supported on a very large area} \\ (d)\; \text{our body weight is very large when compared to the area covered by our foot} \end{array}$