Which of the following assumptions would cause the constant growth stock valuation model to be invalid? The constant growth model is given below: P0 = [D0(1 + g)]/[(rs - g)] A. a. The growth rate is negative. B. b. The growth rate is zero. C. c. The growth rate is less than the required rate of return. D. d. The required rate of return is above 30 percent. E. e. None of the above assumptions would invalidate the model.