An internal auditor is assessing whether a vendor onboarding procedure is being followed in all...

Comprehensive and Detailed Explanation:

The purpose of an internal control questionnaire (ICQ) is to determine whether required control activities are formally in place. The most effective way to compile an ICQ is to develop statements reflecting procedure requirements and ask for yes/no responses (A). This ensures responses can be compared consistently across business units. Open-ended (B) or detailed narrative questions (C) are less efficient and harder to standardize. Multiple-choice (D) resembles a test and is not aligned with ICQ’s objective. According to CIA exam guidance, ICQs are designed to confirm the existence and adherence to specified controls. Therefore, Option A is the most suitable.