The reason for the indifference curve being convex to origin is :

diminishing marginal rate of substitution

The correct answer is option (3) : diminishing marginal rate of substitution

Indifference curves represent combinations of goods or services that provide the same level of satisfaction or utility to a consumer.The law of Diminishing Marginal Rate of Substitution causes an indifference curve to be convex to the origin.

• Diminishing Marginal Rate of Substitution (MRS): This principle states that as a consumer substitutes one good for another, the amount of the second good they are willing to give up decreases. In other words, the consumer requires more and more compensation in terms of the other good to be willing to give up one additional unit of the first good.

• Convexity of Indifference Curves: Indifference curves are convex to the origin because of diminishing MRS. As we move along an indifference curve from left to right, the slope of the curve (which represents the MRS) decreases. This reflects the fact that as the consumer has more of one good, they are less willing to trade it for additional units of the other good.