Ford Motor Company had realized returns of $10\%,20\%,-15\%,$ and $-10\%$ over four quarters. What is the quarterly standard deviation of returns for Ford?

A$.14\mathrm{.}04\%$

B$.15\mathrm{.}69\%$

C$.16\mathrm{.}52\%$

D$.14\mathrm{.}87\%$