The arithmetic average return on the S&P $500$ Index is $\_\_\_\_\_,$ and the standard deviation of returns on the S&P $500$ Index is $\_\_\_\_\_.$

a$.$

$13\mathrm{.}33\%$; $15\mathrm{.}25\%$

b$.$

$13\mathrm{.}43\%$; $13\mathrm{.}33\%$

c$.$

$13\mathrm{.}33\%$; $17\mathrm{.}68\%$

d$.$

$13\mathrm{.}43\%$; $17\mathrm{.}89\%$