The average annual return for the S&P $500$ from $1886$ to $2020$ is $10\%,$ with a standard deviation of $20\%.$ Based on these numbers, what is a $95\%$ confidence interval for $2021\text{'}$s returns?

A$.-20\%,40\%$

B$.-15\%,25\%$

C$.-30\%,50\%$

D$.-15\%,35\%$