Final answer:
Auditors are allowed to both use the work of internal auditors for gathering audit evidence and employ them to provide direct assistance under appropriate supervision. Option b is correct.
Step-by-step explanation:
According to AU-C 610 Using the Work of Internal Auditors and AS 2605 Consideration of the Internal Audit Function, auditors may use the work of internal auditors in gathering audit evidence and use internal auditors to provide direct assistance under the direction, supervision, and review of the external auditors.
Therefore, the correct answer to the question is option 2: auditors are permitted both to use the work of internal auditors to gather audit evidence and to engage internal auditors to provide direct assistance.