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)

include all 10 stocks in the portfolio in equal amounts.

B)

include only the stocks that have the lowest volatility at a given expected rate of return.

C)

include only the stocks with the highest correlation.

D)

find the combination of stocks that produces a portfolio with the maximum expected rate of return at a given level of risk.