What type of firing position does a machinegun provide during a Final Protective Line?

The correct choice highlights the role of the machinegun in providing grazing fire across a unit's frontage during a Final Protective Line (FPL). A Final Protective Line is a predetermined line of defense where a unit is expected to engage an enemy force effectively. The machinegun's capability to deliver grazing fire is crucial in this context because it allows for a low angle of fire that targets enemy forces attempting to cross open ground.

Grazing fire minimizes the danger to friendly forces while maximizing the firing range and effectiveness against an advancing enemy. It sweeps the area with a high volume of fire, creating a formidable barrier that can deter or stop an attack. The machinegun is ideally suited for this role due to its sustained rate of fire and capability to cover large areas.

In contrast, the other options do not appropriately reflect the specific functions of a machinegun in this context. Intermittent firing does not provide the sustained coverage necessary for an effective FPL. Close support for advancing infantry is typically more about direct fire from other weapons systems rather than the sweeping fire characteristic of machineguns. Aerial bombardment implies reliance on air assets, which is not the function of ground-mounted machinegun positions during a FPL.