Which of the following is not a property of double integration?

• A. ∬ af(x,y)ds = a∬ f(x,y)ds, where a is a constant
• B. ∬ (f(x,y)+g(x,y))ds = ∬f(x,y)ds+ ∬g(x,y)ds
• C. \(∬_0^Df(x,y)ds = ∬_0^{D1}f(x,y)ds+ ∬_{D1}^{D2}f(x,y)ds,\) where D is union of disjoint domains D1 and D2
• D. ∬(f(x,y)*g(x,y))ds = ∬f(x,y)ds*∬g(x,y)ds