Q.Choose the correct option: Indifference curves are:

Indifference curves are convex to the origin, reflecting a diminishing marginal rate of substitution. …

Indifference curves are (b) convex to the origin. (a) Concave to the origin is incorrect — a concave shape would imply an INCREASING marginal rate of substitution, meaning a consumer would be willing to give up MORE of Y for each successive unit of X, the opposite of normal, well-behaved preferences. (c) Straight lines with a constant slope is incorrect — that shape describes PERFECT SUBSTITUTES, a special case, not the general/normal indifference curve. (d) Upward sloping is incorrect — an upward-sloping curve would mean a consumer could have MORE of both goods and stay equally satisfi …

Students sometimes confuse the SHAPE of a normal indifference curve (convex) with the special-case straight-line shape of perfect substitutes, especially if they memorise a sing …