The correct answer is: A. The marginal utility of the two goods consumed is equal.
The consumer is in equilibrium, maximizing his total utility, when the marginal utility of the two goods consumed is equal. This means that the consumer is getting the same amount of satisfaction from each good. If the marginal utility of one good is higher than the marginal utility of the other good, the consumer will want to consume more of the good with the higher marginal utility. This will continue until the marginal utilities of the two goods are equal.
Option B is incorrect because the proportion of the marginal utility and the respective price is not relevant to the consumer’s equilibrium. The consumer only cares about the marginal utility of the goods, not the price.
Option C is incorrect because the consumer getting satisfaction from the consumption is not enough to ensure that he is in equilibrium. The consumer must also be getting the same amount of satisfaction from each good.
Option D is incorrect because the consumer being satisfied with his expenditure on various goods is not enough to ensure that he is in equilibrium. The consumer must also be getting the same amount of satisfaction from each good.