What happens when indifference curves are bowed in toward the origin?

Select one:

a.A consumer is more willing to trade away goods when his income increases.

b.A consumer is more willing to trade away goods that he has in abundance than the goods

that he has little of.

c.A consumer is less willing to trade away goods that he has in abundance than the goods

that he has little of.

d.A consumer is less willing to trade away any goods when his income decreases.