The correct answer is A. Marginal rate of substitution.
The marginal rate of substitution (MRS) is the rate at which a consumer is willing to give up one good in exchange for another good, while maintaining the same level of satisfaction. It is measured as the ratio of the marginal utility of the two goods.
The indifference curve is a graph that shows all the combinations of goods that a consumer is indifferent between. The slope of the indifference curve is equal to the marginal rate of substitution.
The establishment rate of trade off is not a term that is used in economics.
The trade off rate is the rate at which one good can be exchanged for another good. It is equal to the reciprocal of the marginal rate of substitution.
The marginal rate of neutrality is not a term that is used in economics.