The correct answer is B because the actions described are classic anti-forensics techniques. CHFI v11 explicitly covers anti-forensics as a major topic and includes examples such as data and file deletion, trail obfuscation, artifact wiping, overwriting data or metadata, steganography, encryption, alternate data streams, and other methods intended to frustrate evidence recovery or analysis. The key clue in the question is that the attacker is not merely damaging systems, but deliberately reducing the quantity, quality, and reliability of digital evidence. That is the defining purpose of anti-forensics. Brute-force techniques are aimed at guessing credentials or cracking protections, not concealing traces. Disk degaussing is a specific media-erasure method, not the broader class of conduct described here. Bypassing techniques is too vague and does not capture the forensic-evasion purpose. In CHFI exam logic, whenever the scenario involves deleting artifacts, manipulating timestamps, altering logs, or hiding content to impair an investigation, the correct classification is anti-forensics. This fits directly under the CHFI v11 blueprint area that addresses anti-forensics techniques and the challenges they create for investigators.