The correct answer is: A. He is responsible for work performed by the assistants.
An auditor is responsible for the work performed by his assistants, even if he delegates the work to them. This is because the auditor is ultimately responsible for the quality of the audit work. The auditor should ensure that his assistants are qualified and competent to perform the work, and that they have a clear understanding of the auditor’s instructions. The auditor should also monitor the work of his assistants and review their work product.
Option B is incorrect because the auditor is always responsible for the work performed by his assistants, even if he delegates the work to them.
Option C is incorrect because the auditor is always responsible for the work performed by his assistants, even if he has taken written permission from the management of the company in this regard.
Option D is incorrect because the auditor is always responsible for the work performed by his assistants.