Primary succession takes much longer than secondary succession because it involves?
a. more time for development of a seed bank.
b. redevelopment of the atmospheric gases.
c. time for weathering of rock and development of the soil horizons.
d. colonization by more equilibrium species.

C. time for weathering of rock and development of the soil horizons

Explanation:

The primary succession is the initial colonization of a previously existing ecosystem that has been totally destroyed by some disastrous event. During this colonization, the organisms that settle in are ones that do not have any particular requirements for their survival, like the lichens and mosses. As they spread all over the area, they slowly start to influence the rocks on which they have grown, little by little weather them and providing them with organic matter. This gives rise to the first soil horizon, but it is very shallow and the soil is not well formed, so lot of time needs until the soil becomes suitable enough for the secondary succession to occur. When the secondary succession occurs it means that there's soil formed in the area, so new organisms move in, and as they do they replace the ones from the primary succession, slowly forming a new ecosystem and well balanced ecological community.