A source from which organisms generally take elements is called

A source from which organisms generally take elements is called exchange pool (option B).

Explanation:

Options for this question are:

The term exchange pool is related to the biogeochemical cycles that exist in nature, referring to the source from which elements present in the environment become part of living organisms.

Exchange pools are the biotic components -like animals and plants- of an ecosystem, which determine the passage of elements between living beings. An element can remain as a reservoir (abiotic) in the soil, and then be incorporated into the exchange pool.