Earthworms and frogs breathe through their skin because of which the skin of both the organisms is

Question

$\begin{array}{1 1} (a)\; \text{Moist and rough} \\ (b)\; \text{Dry and rough} \\ (c)\; \text{Dry and slimy} \\ (d)\; \text{Moist and slimy} \end{array}$