Answer:
a) Determination of whether the client's financial statement assertions are fairly stated in accordance with GAAP.
Step-by-step explanation:
The essential purpose of the external audit function is that the financial statement of the client does not contain any mislead statements, give true and fair value of assurance to the external auditor, follow accounting principles called GAAP.
It checks that client business run in a smooth manner or not which represents legal compliance, industry compliance, etc. Moreover, it also detects the error or fraud, if any.