Which of the following statements is true? a. Increases in a country's endowments of land, labor, and capital will lead to long-run economic growth . b. Improvements in the technology used in production can lead to increases in current output levels, but will not affect long-run economic growth. c. Improvements in production technology do not affect the shape or position of the production-possibility curve. d. Biased growth leads to a proportionate shift in the production -possibility curve.