The correct answer is D (An authorized off-site company resource) because CCPS emphasizes that serious incident investigations—especially those involving fatalities or major consequences —should be led by an individual who is independent, unbiased, and highly trained in investigation methodologies .

An off-site resource provides objectivity and impartiality , which is critical when investigating high-severity incidents. Internal personnel such as the plant manager (A), maintenance supervisor (B), or lead process engineer (C) may have direct or indirect involvement , organizational bias, or conflicts of interest that could influence findings or limit openness during interviews.

Option E (contractor representative) is also not appropriate as a leader due to potential bias and limited system-wide perspective.

CCPS guidance stresses that investigation leaders should have expertise in root cause analysis techniques , strong facilitation skills, and the authority to conduct a thorough and credible investigation. Independence helps ensure that findings focus on system failures rather than individual blame , aligning with a just culture approach.

While internal personnel should be part of the investigation team for technical input, leadership by an independent, qualified individual enhances credibility, ensures rigor, and supports organizational learning and prevention of future incidents.