A firm within the defense industry has been directed to comply with contractual requirements for encryption of a government client's Controlled Unclassified Information (CUI). What encryption strategy represents how to protect data at rest in the MOST efficient and cost-effective manner? Answer with explanation

APerform physical separation of program information and encrypt only information deemed critical by the defense client

BPerform logical separation of program information, using virtualized storage solutions with built-in encryption at the virtualization layer

CPerform logical separation of program information, using virtualized storage solutions with encryption management in the back-end disk systems

DImplement data at rest encryption across the entire storage area network (SAN)