Your Cloud Storage data lake has raw, processed, and historical data in different buckets.

Object Lifecycle Management (OLM) is the correct and fully managed feature in Cloud Storage designed to automate transitions between storage classes and object deletion based on rules like object age, which directly addresses the scenario's requirements for cost control and retention policy.

Cost Control and Rarely Accessed Data: The Archive storage class offers the lowest storage cost, which is ideal for data accessed less than once a year (data older than two years is "rarely accessed"). OLM can automate the move to this class.

Retention Policy: OLM rules can include a Delete action based on a condition like object age, ensuring the "no longer than seven years" retention policy is enforced automatically.

Correcting other options:

A (Custom Script): This is a custom, unmanaged, and potentially complex solution that would require maintenance and incur Compute Engine costs. OLM is the native, fully managed feature.

C (Autoclass): Autoclass automatically manages storage classes to optimize costs, but it generally defaults to Standard for new uploads and transitions data based on access patterns. While it is a managed service, explicitly defining a rule with a deletion policy (after seven years) and the specific transition at two years is best achieved and guaranteed with an OLM rule.

D (Replication): Replicating to a different region increases complexity and typically incurs data transfer and duplicate storage costs, which works against the goal of controlling rising storage costs.