正解:B
During the Detection and Analysis phase of incident response, the primary objective is to validate alerts to determine whether they represent a genuine security incident, and to estimate the scope of the incident to understand the potential impact on the organization. This phase involves analyzing evidence, confirming the nature of the incident, and gathering the necessary information to move forward with containment and remediation.
Developing and updating incident response policies is important but occurs more during the preparation phase, not during the detection and analysis of an active incident. Performing detailed forensic investigations typically takes place during later phases, such as Containment, Eradication, & Recovery or Post-Incident Analysis. Implementing network segmentation and isolation may be part of the Containment phase but is not the primary focus during the Detection and Analysis phase.