If Your Marginal Rate of Substitution Between Two Goods Diminishes

Multiple Choice

If your marginal rate of substitution between two goods diminishes continuously as you give up one good for the other, that means the

A) two goods are perfect complements.
B) two goods are perfect substitutes.
C) two goods are neither perfect substitutes nor perfect complements.
D) price per unit of one good declines when you buy it in larger and larger quantities.