Final answer:
Money used to purchase machinery represents capital in the options provided. Capital includes assets used in the production of goods and services, like machinery and buildings.
Step-by-step explanation:
Capital is a factor of production that refers to the goods that are used to produce other goods and services. Within the options provided, b) Money used to purchase machinery is an example of capital. This is because machinery is used in the production process to generate other products or services. Capital can include physical assets like machinery, tools, and buildings. In this context, capital is not the money itself, but the assets that money can purchase which are then used in the production cycle. Skilled labor and entrepreneurial talent are important parts of the production process, but they represent labor and entrepreneurship, respectively, rather than capital.