Which stage of a product's life involves the customer using the product?

The stage of a product's life that involves the customer using the product is the use stage. This phase is critical because it directly relates to the consumer's interaction with the product, where they utilize its features and functionalities to meet specific needs or solve problems. During this period, the effectiveness, usability, and overall satisfaction with the product become apparent to the customer, often influencing future purchasing decisions and brand loyalty.

The raw materials stage primarily focuses on the sourcing and processing of materials necessary for production, while the manufacturing stage involves turning those materials into finished products. The end of life stage deals with what happens to the product after its useful life is over, including disposal or recycling. These stages, while essential in the overall product development and lifecycle, do not encompass the customer's active usage experience, which is why they are not the correct answer in this context.