42. An investment manager is analyzing 10 possible stocks to include in a client's portfolio. In order to achieve the maximum efficiency of the portfolio, the manager must A. find the combination of stocks that produces a portfolio with the maximum expected rate of return at a given level of risk B. include only the stocks that have the lowest volatility at a given expected rate of return C. include all 10 stocks in the portfolio in equal amounts D. include only the stocks with the highest correlation