Portfolio Theory States That

Portfolio theory states that

A) when investing in securities with yields that are positively related over time,a higher yield can be obtained for the same level of risk for a portfolio as a whole.
B) when investing in securities with yields that are inversely related over time,a given yield can be obtained at a smaller risk or a higher yield can be obtained for the same level of risk for a portfolio as a whole.
C) when investing in securities with yields that are inversely related over time,the risk level will be so low as to make reasonable returns impossible for the portfolio as a whole
D) when investing in securities with yields that are positively related over time,the investor's level of risk will be so great as to discourage most investors from entering the market