Identifying Volatility in Investment Portfolios

In a recent analysis of three investment portfolios, the following annual returns (in percentage) were recorded over the last five years:

Portfolio A: 5%, 7%, 6%, 8%, 10%

Portfolio B: 1%, 1%, 2%, 1%, 1%

Portfolio C: 15%, 12%, 10%, 8%, 20%

Using the data provided, calculate the standard deviation of the annual returns for each portfolio. The measure of dispersion that best indicates the volatility of these portfolios will be which of the following?