Correct sequence of succession on a bare rock is

Question

$\begin{array}{1 1} a.Lichens \to Mosses \to Grasses \to Shrubs \to Trees \\ b. Trees \to Shrubs \to Lichens \to Mosses \to Grasses \\ c. Mosses \to Shrubs \to Trees \to Lichens \to Grasses \\ d. Mosses \to Lichens \to Grasses \to Shrubs \to Trees \end{array} $