In X++, the index keyword in a select statement instructs the database to use a specific index to retrieve records. Because the VehicleIdIdx is a clustered index on the VehicleId field, selecting via this index automatically retrieves the records in the physical order of that index. In SQL Server (which backs Dynamics 365), a clustered index sorts data in ascending order by default. Therefore, select vehicle index VehicleIdIdx; is the most efficient way to fulfill the requirement of retrieving all records in ascending order of VehicleId without the overhead of an explicit order by clause.

B. select vehicle order by VehicleId desc; This statement retrieves records in descending order, which directly contradicts the requirement for ascending order specified in the prompt.

C. select VehicleId from vehicle order by VehicleId asc; This uses invalid X++ syntax. In X++ embedded SQL, you do not use the from keyword; the table buffer itself acts as the source.

D. select vehicle order by VehicleIdIdx desc; This is syntactically incorrect. The order by clause must reference field names, not index names. Additionally, it specifies descending order.

Microsoft Learn (Official Documentation): Select Statements Syntax, Section: "Index Clause". Describes how the index hint fetches records in the order defined by the index.

Microsoft Learn (Official Documentation): X++ SQL Selection, Section: "Order By". Confirms that order by must use field names, not index identifiers.

Microsoft Dynamics 365 Implementation Guide: Database Best Practices. Explains that utilizing a clustered index for sorting is the performant standard for retrieving ordered data sets.

Inside Microsoft Dynamics AX (Technical Reference): Chapter 5: Data Access. Details the behavior of the X++ compiler regarding table buffers and embedded SQL syntax requirements.