Final answer:
An independent auditor can best assess the objectivity of an internal auditor through their adherence to professional auditing standards, ensuring integrity and impartiality.
Step-by-step explanation:
The given question concerns the assessment of an internal auditor's objectivity by an independent auditor. An internal auditor's objectivity is considered to be higher when they adhere to strict professional auditing standards. Therefore, the correct answer is c. The internal auditor's adherence to professional auditing standards.
The close relationship with top management, reliance on management for promotion opportunities, or involvement in day-to-day operational decisions may potentially hinder objectivity due to conflicts of interest or pressures to conform to management's directives. Adherence to professional standards, in contrast, promotes independence and objectivity by ensuring that the internal auditor is governed by a framework designed to maintain integrity and impartiality in the auditing process.