Which of the following is the best way for an internal auditor to demonstrate due...

The best way for an internal auditor to demonstrate due professional care is to conduct an audit to the same extent that another prudent auditor would under similar circumstances. This involves applying the knowledge, skills, and judgment expected of an auditor in comparable roles or situations, ensuring thoroughness and appropriateness in the conduct of the audit work, and adhering to professional standards and ethical guidelines.

The IIA's International Standards for the Professional Practice of Internal Auditing on due professional care.