Final answer:
The slope of an indifference curve is known as the marginal rate of substitution, representing the rate at which a person is willing to trade one good for another while keeping utility constant. It reflects the consumer's willingness to substitute between goods in response to changes in relative prices. (option a)
Step-by-step explanation:
The magnitude of the slope of an indifference curve is the marginal rate of substitution. This represents the rate at which a consumer is willing to trade off one good for another while maintaining the same level of utility. Indifference curves depict consumer preferences and typical characteristics include being downward sloping from left to right and convex to the origin.
This reflects the idea that as a consumer substitutes one good for another, they must give up increasingly smaller amounts of one good to gain extra units of the other, holding utility constant.
The substitution effect within consumer theory illustrates how changes in prices, while holding utility constant, lead to changes in the consumption pattern. As a more expensive good's consumption decreases, a less expensive good's consumption increases. This movement along an indifference curve from one point to another (e.g., from point A to point C) due to a change in relative prices is captured by the slope, or the marginal rate of substitution, at any given point on the curve.
Hence, the answer is option a