问题详情

The most fundamental proposition of modern portfolio theory can be stated as follows:
A．people are all risk averse
B．an asset may be very risky when viewed in isolation, but when combined with other assets the risk of the portfolio may be substantially reduced
C．the returns on securities are interrelated, and therefore a measure of their covariability must be used when combining securities in portfolios
D．none of the above请帮忙给出正确答案和分析，谢谢！