During an external audit of an organization's financial statements.

 Auditor's Responsibility Under ISA Standards:

ISA 265 requires auditors to communicate significant deficiencies in internal control to those charged with governance in writing.

This ensures proper corrective actions are taken and maintains transparency in the audit process.

 Why B is Correct:

Written communication to governance authorities is the appropriate course of action to address control deficiencies without breaching confidentiality or overstepping regulatory boundaries.

 References:

ISA 265, “Communicating Deficiencies in Internal Control,” supports this approach​​.