A key characteristic of the production function in the endogenous growth model presented in the text is that

A.

there are decreasing returns to scale in human capital.

B.

there are increasing returns to scale in human capital.

C.

at low levels of humancapital, there are increasing returns to scale in humancapital, while at high levels of humancapital, there are decreasing returns to scale in human capital.

D.

there are constant returns to scale in human capital.

E.

there are substantial diminishing marginal returns to human capital.