You want to estimate the volatility of returns for the S&P $500$ for the past three years based on the following information.

S&P$500$ return in $2012$: $16\%$

S&P$500$ return in $2013$: $31\%$

S&P$500$ return in $2014$: $13\%.$

Arithmetic average of S&P$500$ return in $2012-2014$: $20\%.$

The estimated volatility of returns is closest to:

A$.1\mathrm{.}9\%.$

B$.7\mathrm{.}9\%.$

C$.9\mathrm{.}6\%.$

D$.13\mathrm{.}6\%.$