If an investor does not diversify his portfolio and instead puts all of his money in one stock, the appropriate measure of security risk for that investor is the ________. If the investor considers adding one stock to a market index fund, the appropriate measure of security risk for that investor is the ________.

A.stock's standard deviation; standard deviation of the market

B.stock's beta; standard deviation of the market

C.standard deviation of the market; stock's beta

D.stock's standard deviation; stock's beta;

E.stock's beta; stock's standard deviation