Which statement leads to a syntax error when working with an ABAP structured data object?

A syntax error occurs in ABAP when the language rules are not followed properly in the code. In this scenario, the focus is on the manipulation of structured data objects.

The correct statement among the choices is that "none" leads to a syntax error. This implies that both of the provided statements can be executed correctly without causing any syntax issues. In ABAP, structured data types can be manipulated using the dot notation where the field names of the structure are referenced directly.

The statement assigning a value to struct-airlineid is a straightforward assignment that properly adheres to the syntax rules for accessing fields in a structure.

On the other hand, the statement using struct-%tky-airlineid appears to be incorrect due to the inclusion of the percent sign. However, in certain contexts, especially when variables (data references) are used, ABAP may allow such patterns, especially when dealing with dynamic field names or fields of a generic structure. Hence, it does not inherently produce a syntax error.

In summary, both methods of accessing fields within a structured data object in ABAP are valid under the language rules up to October 2023. This is why stating that none of them lead to a syntax error is the accurate choice