Which expression is the correct factorization (reverse of distribution) of 12x + 6y - 21z?

• A. No common factor; expression is already fully factored and cannot be expressed as a product with integer coefficients
• B. 6(2x + y - 10.5z)
• C. 3(4x + 2y - 7z)
• D. 12(x + 0.5y - 1.25z)

Answer: (C)