Which of the following expressions is necessarily equal to 1?
(f(x, y, z) – m(x, y, z))/(g(x, y, z) – h(x, y, z))
(m(x, y, z) – f(x, y, z))/(g(x, y, z) – n(x, y, z))
(j(x, y, z) – g(x, y, z))/h(x, y, z)
(f(x, y, z) – h(x, y, z))/f(x, y, z)