Suppose that f(x) is a continuous function over all real numbers, K f'(9) = 0, and f"(9) = 20 Which of the following is true? (Hint: 2nd derivative test) O A. f(x) has a relative minimum at x = 9 O B. f(x) is increasing when x = 9 O C. f(x) has a relative maximum at x = 9 O D. f(x) is decreasing when x = 9 O E. None of the above