The Standard Deviation of a Portfolio

The standard deviation of a portfolio:

A) is a measure of that portfolio's systematic risk.
B) is a weighed average of the standard deviations of the individual securities held in that portfolio.
C) measures the amount of diversifiable risk inherent in the portfolio.
D) serves as the basis for computing the appropriate risk premium for that portfolio.
E) can be less than the weighted average of the standard deviations of the individual securities held in that portfolio.