Volume of a sphere = 4/3 × πr³. Substitute r=6: volume = 4/3 × 3.14 × 6³ = 904.32 cubic mm. A sphere is a fully round solid, so its volume depends on the cube of the radius, r³. Cubing the radius means multiplying the radius by itself three times before applying 4/3π. The answer is in cubic units, so the correct choice is 904.32 mm³.