In any ecosystem, terrestrial or aquatic, what group (s) is (are) always necessary?; a) autotrophs and heterotrophs; b) producers and primary consumers; c) photosynthesizers; d) autotrophs; e) green plants

I think the correct answer from the choices listed above is option B. In any ecosystem, terrestrial or aquatic, the groups that are always necessary to be present would be producers and primary consumers. They are most likely the foundations of an ecosystem. Hope this answers the question.