Final answer:
The size of the internal audit department is typically the least important factor in determining reliance on the work of internal auditors, compared to independence, certifications, and report frequency.
Step-by-step explanation:
To determine how much reliance can be placed on the work of internal auditors, an auditor would consider various factors. Of the options provided, the size of the internal audit department would generally be of least importance compared to the other factors. Independence and objectivity are crucial for internal auditors to provide unbiased assessments. Professional certifications indicate the knowledge and expertise of the audit staff which can affect the quality of their work. The frequency of internal audit reports may impact the timeliness of information, but not necessarily the reliance on the work performed. Therefore, while all factors could have some impact, the size of the department is the least indicative of the internal auditors' work quality and reliability.