The Marginal Physical Product of Labor Increases When More Laborers

The marginal physical product of labor increases when more laborers are added to production, although it eventually falls as laborers are continually added. The explanation for the initial increase is the

A) low wage rates at the beginning of production
B) more skilled labor at the beginning of production
C) marginal revenue product is less than the marginal physical product
D) marginal revenue product decreases at every production level
E) gains from the division of labor and specialization