Which factor is NOT part of a supply chain in marketing?

The correct choice highlights that shareholders are not typically considered a part of the supply chain in marketing. The supply chain generally refers to the entire process involved in delivering a product or service to the end consumer, which includes various stakeholders directly engaged in the tangible and logistical aspects of production, distribution, and sales.

Suppliers provide the raw materials needed for production, which is the first step in the supply chain. Retailers play a crucial role in selling the product to the end consumer, often serving as the last touchpoint before the product reaches them. Distributors are involved in the logistics of moving products from manufacturers to retailers or directly to consumers, facilitating the flow of goods within the supply chain.

While shareholders are vital to a company's financial health and strategic direction, they typically do not engage in the operational processes involved in the supply chain. Their interests lie more in the financial performance and returns on investments rather than the mechanics of product distribution and sales, which distinguishes them from the other three options.