Which one of the following is the set of portfolios that provides the maximum return for a given standard deviation?

An efficient portfolio is a portfolio that does which one of the following? A. offers the highest return for the lowest possible cost B. provides an evenly weighted portfolio of diverse assets C. eliminates all risk while providing an expected positive rate of return D. lies on the vertical axis when graphing expected returns against standard deviation E. offers the highest return for a given level of risk O offers the highest return for the lowest possible cost O provides an evenly weighted portfolio of diverse assets O eliminates all risk while providing an expected positive rate of return O lies on the vertical axis when graphing expected returns against standard deviation O offers the highest return for a given level of risk