In what scenario might an auditor decide to expand their testing during an audit?

An auditor may decide to expand their testing during an audit in the scenario where significant discrepancies are found. This is a critical aspect of the audit process, as such discrepancies may indicate deeper issues that could affect the accuracy and reliability of financial statements or compliance with regulations. When significant discrepancies emerge, they can suggest potential fraud, errors, or weaknesses in internal controls, which necessitates a more thorough examination to ensure that the organization's financial reporting is accurate and that risks are properly managed.

By expanding testing in response to these discrepancies, auditors can obtain additional evidence to understand the nature and extent of the issues, assess their impact, and determine whether additional controls are needed. This helps in forming a more comprehensive opinion on the financial statements and overall compliance, ultimately contributing to the integrity of the audit.

The other choices do not align with the professional judgment required in auditing. Rushing due to time constraints, responding to management requests without a valid basis, or simply completing initial tests do not provide the necessary justification for expanding testing; it is the findings of significant discrepancies that trigger the need for a deeper investigation.