Which of the following statements is true of a portfolio's standard deviation? Multiple Choice It is a weighted average of the standard deviations of the individual securities held in the portfolio. It can never be less than the standard deviation of the most risky security in the portfolio. It is equal to or greater than the lowest standard deviation of any single security held in the portfolio. It is an artithmetic average of the standard deviations of the individual securities which comptise the portfolia. It can be less than the standard deviation of the leost risky security in the portfotio