The rate at which consumer is willing to substitute one good for another is represented by _____.

Slope of indifference curve.

The correct answer is Option (2) → Slope of indifference curve.

The Marginal Rate of Substitution (MRS) is the rate at which a consumer is willing to substitute one good for another while maintaining the same level of satisfaction. It is represented by the slope of the indifference curve at any given point. As the consumer moves along the indifference curve, the MRS tells us how much of one good the consumer is willing to give up to gain an additional unit of the other good.