If the auditor believes that the financial statements are not fairly stated or is unable to reach a conclusion because of insufficient evidence, the auditor:
a. should request an increase in audit fees so that more resources can be used to conduct the audit.
b. should notify regulators of the circumstances.
c. has the responsibility of notifying financial statement users through the auditor's report.

C. has the responsibility of notifying financial statement users through the auditor's report.

Explanation:

Auditor responsibility: The responsibility of the auditor is to give the true and fair opinion on the company's financial statements. The checking of an error or any fraud done by the company is checked by the auditor and the same is communicated to the users of the financial statement.  

If all the things are fine than the auditor gives the unqualified opinion else it gives the qualified opinion.

Thus, all other statements are incorrect because it is against the rules and regulations, so if the statement is not fairly stated or the evidence is insufficient to reach any conclusion, the auditor has to notify the users of the financial statement through the auditor's report.

by knowing conditionality

explanation: