B is correct because Nearline Storage is designed for infrequently accessed data, offering a cost-effective solution for data accessed about once a month. C is correct because deleting data that is no longer needed after 2 years is the most efficient way to reduce storage costs, and this can be automated with a lifecycle policy. Options involving transitioning to Coldline or Archive storage are incorrect since the data is not needed after 2 years, making deletion the appropriate action. Storing infrequently accessed data in a Multi-Regional bucket is not cost-effective for this scenario.