The values of \(x\) and y are such that \(f(x) = f(2y)\) for a certain function \(f\). Which of the following is equivalent to \(f(x) + f(x)\) ? I. \(2f(2y)\) II. \(f(4y)\) III. \(2 (f(y) + f(y))\)
(A)I only (B)II only (C)I and III (D)II and III (E)I, II, and III
A