The correct answer would be option D, Not affected by.
People keep spending addition units of a particular resource on a want until their marginal benefit is not affected by their marginal cost.
Explanation:
Marginal cost and Marginal benefit are the economic concepts used in businesses to a greater extent.
Marginal cost is the cost or amount of money which is added in order to produce one additional unit of a particular product.
Marginal Benefit, similarly, is the benefit or profit gained by producing one additional unit of a particular product.
So people keep spending additional units of resources on producing the product until their marginal benefit is not affected by their marginal cost.
Learn more about Marginal benefit and Marginal Cost at:
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