Current research suggests that the substance is an endogenous ligand for cannabinoid recepto

anandamide

Explanation:

Current research suggests that the substance anandamide is an endogenous ligand for cannabinoid receptors.

d is the correct answer.

b is incorrect because it makes food by itself

c is incorrect because us humans don't know how to produce their own food using the sun like plants.

a is incorrect because consumers can depend on carnivores for eating food for consumers to eat the dead organism. same thing with omnivores.

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