Final answer:
The METT-TC factor at the root of the question 'Can the ground support access by an EOD vehicle?' is the 'terrain' factor.
Step-by-step explanation:
The METT-TC factor at the root of the question 'Can the ground support access by an EOD vehicle?' is the 'terrain' factor. METT-TC stands for Mission, Enemy, Terrain and weather, Troops and support available, Time available, Civil considerations. In this case, the terrain factor refers to the physical characteristics of the ground, such as its stability, slope, and load-bearing capacity, that determine whether it can support the weight and movement of an EOD (Explosive Ordnance Disposal) vehicle.