The best answer is C because the scenario involves several different anti-forensic tactics at once rather than one isolated concealment method. Concealed payloads, wiped artifacts, and timestomping each require different technical responses, so the most effective overarching countermeasure is to ensure investigators are trained to recognize and respond to a broad range of anti-forensic techniques. CHFI v11 covers anti-forensics techniques, the challenges they create, and countermeasures, and exam questions often distinguish between a tool for one problem and a broader capability that improves the entire investigation. Option A helps with deleted or overwritten data, option B addresses hidden content such as steganography, and option D targets packed or obfuscated material. All are useful, but each is narrow. The question asks what should be prioritized to enhance reliability and thoroughness without relying on a single method. That wording points to investigator awareness and education as the cross-cutting countermeasure that enables the team to choose the right technical method for each evasion tactic encountered. Therefore, training and educating investigators about anti-forensic techniques is the strongest answer.