An experienced internal auditor is planning an assurance engagement of the organization's sales activities.

The best application of due professional care in planning the engagement is to consider the significance of the risks related to the complaints and develop appropriate assurance procedures in work programs. This approach ensures that potential risks are evaluated and addressed systematically.

Option A: Disregarding the complaints without evaluating their significance is not consistent with due professional care.

Option C: Using complaints as input for risk assessment does not violate confidentiality principles.

Option D: While discussing with management is important, it is more crucial to independently evaluate the risks and plan appropriate procedures.

IIA Standard 1220: Due Professional Care.

IIA Practice Guide: Assessing Organizational Governance.