Which scenario would require an inventory according to common standards?

An inventory is required when there is a change of Personnel Higher Responsibility Holder (PHRH) because this shift in responsibility necessitates a complete accounting of the assets. The outgoing PHRH must ensure that all property and equipment are accounted for, documented, and confirmed as being handed over to the incoming holder. This process helps maintain accountability and integrity in property management, ensuring that all military property is accurately tracked and that there are no discrepancies in the records.

The other scenarios, while important for various operational and administrative reasons, do not inherently require a formal inventory process. Scheduled training exercises may involve the use of military property but do not necessitate a formal evaluation of property accountability. Completing a report is associated with data management but does not trigger a requirement for an inventory. Monthly maintenance checks focus on the upkeep and operational readiness of equipment rather than confirming the overall inventory of assets. Thus, the scenario involving a change of PHRH stands out as the one that mandates a thorough inventory process according to common standards.