Which one of the following operates at the session, transport, or network layer of the Open System Interconnection (OSI) model?

Data at rest encryption protects stored data and is not associated with any specific OSI layer, as it is an application- or storage-level control that operates outside the OSI transmission model.

Configuration Management is an administrative and operational process concerned with tracking and controlling system configurations, and it does not map to any specific OSI layer.

Integrity checking software (e.g., file hash verification tools) operates at the Application Layer (Layer 7) of the OSI model, not at the session, transport, or network layers.

Cyclic Redundancy Check (CRC) is an error-detection algorithm used at the Data Link Layer (Layer 2) and Network Layer (Layer 3) of the OSI model to verify the integrity of transmitted frames and packets. It is embedded directly into network protocols (e.g., Ethernet frames) and hardware to detect accidental changes to raw data during transmission. Among the choices, CRC is the only mechanism that operates natively within the lower-to-mid OSI layers (network, data link, and transport contexts), making it the correct answer.