The correct answer is: D. Preference rule
An indifference curve is a graph that shows all the combinations of goods that a consumer is indifferent between. In other words, the consumer is equally satisfied with any combination of goods on the curve.
Indifference curves cannot intersect each other because it would violate the preference rule. The preference rule states that a consumer prefers a combination of goods A to a combination of goods B if and only if the consumer is not indifferent between A and B. If indifference curves could intersect, then it would be possible for a consumer to be indifferent between two combinations of goods, even though one combination contains more of one good and less of the other good. This would violate the preference rule.
The transitivity rule states that if a consumer prefers A to B and B to C, then the consumer must prefer A to C. This rule is necessary to ensure that the indifference curves are consistent with the consumer’s preferences.
The optimal rule states that a consumer will always choose the combination of goods that gives them the most satisfaction. This rule is necessary to ensure that the indifference curves are consistent with the consumer’s behavior.
The non-satiety rule states that a consumer will always prefer more of a good to less of a good. This rule is necessary to ensure that the indifference curves are consistent with the consumer’s desires.