The correct answer is D (Coldline). Coldline storage is specifically designed for scenarios like disaster recovery where data is accessed infrequently, if at all. It offers a cost-effective solution with high durability and quick access when needed. This makes it ideal for storing backup data that is only required in the event of a disaster.

• Multi-regional (A) and Regional (B) are more suited for data that requires frequent access and higher availability.
• Nearline (C) is a better fit for data accessed once a month or less, but not as cost-effective as Coldline for very rarely accessed data.

Coldline Storage ensures your disaster recovery data is stored at a very low cost, with the data being available within milliseconds when needed, unlike other cold storage services that may take hours or days. It's the optimal choice for infrequently accessed data, such as disaster recovery backups, due to its pricing structure and access costs.