Lichens are the association of
(a) An autotroph and a saprotroph
(b) An autotroph and a heterotroph
(c) A green plant and non-green plant
(d) All the above

Lichens have a symbiotic relationship between algae and fungus hence they are called dual organisms.

Lichens grow from the substrate of fungi in an algae environment.

The algae and fungi are in a mutual relationship where algae help to produce food and fungus help to absorb the nutrients. Lichens are of various sizes and forms, divided into thallus and filament body parts.

Lichens are of a variety of colors due to the presence of usnic acid.