Which of the following is directly related to the stability of a product?

The expiration date is directly related to the stability of a product because it indicates the period during which the product is expected to maintain its intended quality, safety, and efficacy. Stability testing is conducted to determine how long a product can be expected to perform without degradation under specified conditions, which is then used to establish the expiration date. This date is critical for ensuring that consumers use the product when it is most effective and safe.

While the manufacturing date reflects when the product was produced, it does not provide information about how long the product will remain stable or effective. Packaging type can influence stability, as certain materials may provide better protection against environmental factors, but it does not directly convey the ultimate point at which a product may no longer be safe or effective. Storage temperature affects how quickly a product may degrade, but the expiration date is the final guideline for users regarding the product's stability and usable life.