Human-capital theory suggests that A) the growth rate in earnings tends to be smaller the more educated a person becomes because of diminishing marginal returns. B) the decision to be absent from the labor force reduces an individual's earnings, not only for those years absent from the labor force but for all subsequent years as well. C) tuition payments and foregone earnings are not important when calculating the net present value of human capital investments. D) both (A) and (B). E) all of the above.