50. Which of the following is NOT necessarily true about a real-valued function f(x)?:* O (A) If fox) is differentiable at x = 3, then f(x) is continuous at x = 3. O (B) If f ' (3) = 0, then f(x) has an absolute maximum or absolute minimum at x = 3. O (C) If fix) is differentiable at x = 3, then g(x) = (fx)* is differentiable at x = 3. O (D) All of the above are always true