What is the Marginal Rate of Substitution(MRS)?

(A) The rate at which a consumer is willing to substitute one good for another.

(B) Equal to the slope of the indifference curve.

(C) Changes as we move along the indifference curve.

(D) Is constant for perfect substitutes.

Choose the correct answer from the options given below:

Option 1 -> Includes statements (A), (B), and (D) which are universally true characteristics of MRS.

Option 2 -> Includes statement (C) which is not universally true as MRS remains constant for perfect substitutes.

Option 3 -> Includes all statements including (C), which contradicts statement (D) since MRS doesn't change for perfect substitutes.

Option 4 -> Excludes statement (A) which is the fundamental definition of MRS, making this incorrect.

Hence, Option 1: (A), (B) and (D) only -> Statement (A) defines MRS as the willingness to substitute goods. Statement (B) correctly identifies MRS as the slope of the indifference curve (absolute value). Statement (D) is accurate for perfect substitutes where indifference curves are straight lines with constant slope. Statement (C) is excluded because it's not universally true - while MRS changes along typical convex indifference curves due to diminishing marginal rate of substitution, it remains constant for perfect substitutes, making (C) and (D) contradictory if both were included. -> correct