select the statement that is most correct?

A, proper diversification can reduce or eliminate systematic risk?

B, the risk reduce benefits of diversification do not occur meaningful until at least 10 to 15 individual securities have been purchased

C, because diversification reduce a portfolios total risk, it necessary reduce the portfolios expect return.

D, Typically as more securities are added to a portfolio, total risk would be expected to fall at a decreasing rate.

E, All of them above.