Which of the following statements are CORRECT concerning a portfolio? I. A portfolio's beta takes value between -1 and +1. II. A portfolio's standard deviation is the weighted average of the standard deviations of the individual securities contained in the portfolio. III. A portfolio's beta is the weighted average of the betas of the individual securities contained in the portfolio. IV. All else equal, if the correlation between two assets is higher, then the standard deviation of the portfolio that consists 50% of each of these two assets will be lower. A. I and II only B. II and IV only C. III and IV only D. III only E. IV only