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In nature, every organism depends upon others to fulfill its needs. The symbiotic association is a term that involves two organisms living together and both are beneficial to each other. This relationship between two organisms is called a symbiotic relationship.

The association between fungi and cyanobacteria is called lichen. It is a stable association. In this mutual association, fungi absorb minerals and water for the bacteria, and in return cyanobacteria being photosynthetic provides food to fungi.

Mycorrhizae is the association of fungi with the root of the plant.

Epiphytes are the plants that grow on other plants but they make their food.

Nitrogen-fixing nodules are formed when nitrogen-fixing bacteria associate themselves with root nodules of some legume plants.

The correct option is (a).

Lichen is the term used for the association between fungi and cyanobacteria.