问题如下：
Which of the following is incorrect about the risk of an equity security? The risk of an equity security is:
选项：
A.based on the uncertainty of its cash flows.
B.based on the uncertainty of its future price.
C.measured using the standard deviation of its dividends.
解释：
C is correct.
Some equity securities do not pay dividends, and therefore the standard deviation of dividends cannot be used to measure the risk of all equity securities.
考点：Risk And Return, Market Value and Book Value, Required Return
注意股票的风险是股票价格的不确定性，通常股票的风险我们用股票价格标准差来衡量，不是股息的波动幅度。此外很多股票是不分红的，所以没法用红利的标准差来衡量它的风险。
这里的cashflow指的是什么呢？是total return么？
