A stock has yielded returns of $9$ percent, $16$ percent, $12$ percent, and $3$ percent over the past four years, respectively. What is the standard deviation of these returns? A$.9\mathrm{.}60\%$ B$.10\mathrm{.}87\%$ C$.8\mathrm{.}19\%$ D$.8\mathrm{.}78\%$ E$.10\mathrm{.}02\%$