Comprehensive and Detailed Explanation From Exact Extract:

The SRE Book defines the Four Golden Signals of monitoring as Latency, Traffic, Errors, and Saturation. Specifically, it describes “Errors” as: “the rate of requests that fail, whether explicitly, implicitly, or by policy.” (SRE Book – Chapter: Monitoring Distributed Systems). This includes HTTP 5xx responses, timeouts, and requests served but not meeting success criteria.

This definition matches option B exactly.

Option A describes latency, not errors.

Option C describes traffic.

Option D describes saturation (resource usage).

Therefore, B is the correct and SRE-accurate description of the golden signal for errors.