The Slope of an Indifference Curve

The slope of an indifference curve

A) is calculated by dividing the price of good on the vertical axis by price of the good on the horizontal axis.
B) measures total utility.
C) measures the marginal rate of substitution between the two goods in question.
D) is calculated by dividing the quantity of the good on the vertical axis by the quantity of the good on the horizontal axis.