A cold site is a backup facility that provides basic power, space, and environmental controls but does not include hardware or preconfigured systems. It is the organization's responsibility to ensure the site has adequate storage, servers, and equipment staged or available for rapid procurement.
If the cold site "does not have enough storage and computers," the cause is a failure in capacity planning (A).
CompTIA Security+ SY0-701 highlights the need for organizations to determine:
Required compute capacity
Storage needs
Network bandwidth
Expected recovery workload
Hardware replacement timelines
Load balancing (B) distributes traffic; it has nothing to do with cold-site readiness. Backups (C) store data, not physical resources. Platform diversity (D) refers to using multiple technologies to reduce systemic risk.
The issue is specifically the lack of resources, which directly reflects inadequate capacity planning. Therefore, A is the correct answer.