Over the past five months, Amazon stock returns are $5\mathrm{.}21\%,-0\mathrm{.}10\%,-4\mathrm{.}50\%,10\mathrm{.}86\%,$ and $-2\mathrm{.}00\%.$ What is the standard deviation of Amazon returns over the five months?

$6\mathrm{.}15\%$

$23\mathrm{.}24\%$

$1\mathrm{.}8940\%$

$14\%$