Concept:An indifference curve shows combinations of two goods that give a consumer equal satisfaction.Explanation:When a consumer is equally satisfied with different bundles of two goods, these bundles are plotted on a graph.Each point on the curve represents a combination of the two goods that yields the same level of utility.Because the consumer has no preference between the bundles, they are said to be indifferent to them.So the curve drawn through all such combinations is called an indifference curve.Answer:D. indifference curve.