The correct answer is C (Nearline) because the data is accessed only monthly, making Nearline the ideal solution for storage. Nearline is designed for infrequently accessed data, offering a balance between cost and availability. It's perfect for scenarios like monthly disaster recovery drills, backups, and archival storage. For data accessed less than once a year, Coldline would be more cost-effective. Multi-regional and Regional storage options are not optimal for monthly access due to their higher costs and are better suited for frequently accessed data. Nearline's geo-redundancy depends on its storage location, with multi-regional locations offering higher availability than regional ones.