Final answer:
The most likely event to cause an auditor to inquire further about previously issued financial statements is new information concerning undisclosed lease transactions during the audited period. This could indicate potential misstatements in the financial statements that need to be addressed.
Step-by-step explanation:
When considering events that occur after the issuance of a client's financial statements and the auditor's report, auditors need to make further inquiries if the events could potentially affect the financial statements previously issued. Of the options provided, new information discovered concerning undisclosed lease transactions in the audited period is most likely the event that would cause the auditor to make further inquiries. This is because it could indicate that the financial statements may have been misstated, which is a direct concern regarding the integrity of the financial information presented.
An uninsured natural disaster may affect the entity's ability to continue as a going concern, which is a subsequent event requiring disclosure, but not necessarily a trigger to re-evaluate the previous financial statements unless the disaster has immediate retroactive implications. A contingency that had already been disclosed is not a concern unless the resolution affects the prior period's financials materially. The sale of a subsidiary is significant information for upcoming reporting periods and should be addressed in subsequent reports.