Small organisms, such as lichens, break up bare rock into soil. a lichen is an example of a:

succession
primary succession
secondary succession
soil
climax community
pioneer species

Lichens are example of Primary succession and Pioneer species.

Option B & F

Explanation:

The lichens are nothing but combination of two microorganisms called fungi and algae. They survive together based on mutual benefit. Lichens are regularly the main creatures to colonize inhabitant rock.

They are in this manner the pioneer species in primary progression. Numerous life forms require soil before they can colonize a region. Lichens that colonize uncovered rock emit acids that separate the stone and start the dirt creation process.

Additionally, as lichens bite the dust, they give some natural issue that likewise adds to soil. Following this certain other events required for mature forest formation occurs.  

it's diluted or concentrated

in a diluted solution, you can add a lot more solute but in concentrated only a little more can be added