Which formal statement correctly expresses the multiplication property of equality?

• A. If a + c = b + c, then a = b provided c ≠ 0.
• B. If ac = bc, then a = b only when c = 0.
• C. If a = b, then a/c = b/c only when c = 0 and both sides are undefined.
• D. If a = b, then a·c = b·c for any number c.

Answer: (D)