You are developing a Power Platform solution. The solution connects to a third-party accounting system by using a Web API through a Power Apps app that automatically exchanges contacts with the sales data. You have the following code: (Line numbers are included for reference only.) 
You need to ensure that the code only synchronizes data that was not previously synchronized. Which code segment should you insert at line 02?
I don't think it's C. The question's looking for a mechanism to sync only unsynced data, and that's exactly what the odata.track-changes header (A) is designed for-it gets you a delta token so you only pull changes since your last call. Option C is more about entity references, not change tracking. Pretty sure A is right here, but open if someone has a counterpoint.