The Fact That the Market Labor Supply Curve Is Upward

The fact that the market labor supply curve is upward sloping at all wage rates illustrates that

A) all people supply more labor as the wage rate increases.
B) the combined effect of individual labor supply curves results in a greater number of labor hours being supplied at a higher wage rate.
C) the compensating wage differential works.
D) at high wages, people will decrease labor supply when wages rise further and thus make aggregate labor supply decrease.
E) the marginal benefits of leisure decrease as wages increase.