Systems that enable a firm to generate demand forecasts for a product and to develop sourcing and manufacturing plans for that product best describes:

The designation of "supply chain planning systems" aligns perfectly with the described function of generating demand forecasts and developing sourcing and manufacturing plans. These systems are critical in planning the flow of goods and materials to ensure that supply meets anticipated demand. They utilize various data inputs, such as historical sales, market trends, and economic indicators, to create accurate forecasts that help organizations strategize production schedules and procurement activities.

By integrating demand forecasting with sourcing and manufacturing capabilities, supply chain planning systems allow organizations to optimize inventory levels, reduce costs, and enhance service levels. This proactive approach ensures that the right quantity of products is available at the right time, directly contributing to the overall efficiency of the supply chain.

The other choices refer to different facets of supply chain management: delivery systems focus on the logistics and transportation aspects, execution systems are concerned with the implementation of actual operations, and demand systems primarily involve tracking consumer demand rather than planning and forecasting. Thus, the correct identification of supply chain planning systems emphasizes their role in the strategic element of supply chain management, bridging the gap between forecasting and operational execution.