Final answer:
The final phase of an IS life cycle where it loses its value is Retirement. This stage signifies the system's obsolescence or lack of utility, leading to its decommissioning.
Step-by-step explanation:
The last stage of an Information System (IS) life cycle where the system loses its value is a. Retirement. During this phase, the system is considered obsolete or no longer useful due to various factors, such as technological advancements, changes in business needs, or when the system becomes too costly to maintain. At this point, the system is decommissioned, and plans are typically made to transition to a replacement system, if necessary.