Final answer:
During an operational engagement, the internal auditor should report any environmental concerns observed to the organization's environmental safety department and follow up on actions taken, even if the audit scope does not cover environmental issues.
Step-by-step explanation:
The question presented concerns the ethical and professional actions that an internal auditor should take upon noticing potential environmental risks during an operational engagement, even though the engagement scope does not cover environmental concerns.
The best course of action would be C. This option involves the auditor documenting the observations related to the above-ground storage containers and the black emissions and reporting these to the environmental safety department.