What is the nomenclature of the gun?

• A. M61A1
• B. M61A2
• C. M60A1
• D. M61B1

Answer: (A)

Nomenclature of military weapons uses a model number plus a variant suffix to identify the exact item. The M61 is the designation for the 20mm Vulcan rotary cannon, so the full name includes a suffix that points to a specific version. The A1 suffix means the first variant of that model, a naming convention used to distinguish early configurations from later ones.

This is why the designation M61A1 is the best answer: it is the standard way to refer to the gun with its initial variant, matching how these weapons are cataloged and discussed in references. The other options point to either a different weapon altogether (the M60 is a different firearm) or to a variant that isn’t used in the same naming pattern for this gun (M61A2 is a later variant, and M61B1 doesn’t fit the established suffix conventions).