questions 18-21 please and thanks

18. Suppose that a stock portfolio and a bond portfolio have a zero correlation. This means that A. the returns on the stock and bond portfolios tend to move inversely B. the returns on the stock and bond portfolios tend to vary independently of each other C. the returns on the stock and bond portfolios tend to move together D. the covariance of the stock and bond portfolios will be positive E. None of the above 19. Rational risk-averse investors will always prefer portfolios A. located on the efficient frontier to those located on the capital market line B. located on the capital market line to those located on the efficient frontier C. at or near the minimum-variance point on the efficient frontier D. that are risk-free to all other asset choices E. none of the above 20. The values of beta coefficients of securities are A. always positive B. always negative C. always between positive 1 and negative 1 D. usually positive but are not restricted in any particular way E. none of the above risk. 21. Diversification can reduce or eliminate A. all B. systematic C. nonsystematic D. only an insignificant E. None of the above