What Does an Upward-Sloping Labor Supply Curve Mean

Multiple Choice

What does an upward-sloping labor supply curve mean?

A) It means that workers prefer to buy more leisure time when their incomes increase.
B) It means that workers prefer to supply less labor when wages are high.
C) It means that an increase in the opportunity cost of leisure leads workers to increase the quantity of labor they supply.
D) All of the above are correct.