The Explanation for the Upward Sloping Supply of Labor Curve

Multiple Choice

The explanation for the upward sloping supply of labor curve is that:

A) the marginal product of capital is positive.
B) as the wage rises the opportunity cost of leisure rises,so people work more.
C) as the wage rises,people want to work less.
D) the marginal product of labor is diminishing.
E) None of the above is correct.