What Does an Upward-Sloping Supply Curve Mean

Multiple Choice

What does an upward-sloping 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 labour when wages are high.
C) It means that an increase in the opportunity cost of leisure leads workers to increase the quantity of labour they supply.
D) It means that workers will be more productive at higher wages.