1. Improvements in technology. 2. Increases in the supply (stock) of capital goods. 3. Purchases of expanding output. 4. Obtaining the optimal combination of goods, each at least-cost production. 5. Increases in the quantity and quality of natural resources. 6. Increases in the quantity and quality of human resources. Use the accompanying list to answer the following question. As distinct from the demand and efficiency factors of economic growth, the supply factors of economic growth are A) 2, 5, and 6 only. B) 1, 3, and 4 only. C) 2, 4, 5, and 6 only. D) 1, 2, 5, and 6 only.