Peter rolls two standard six-sided dice at the same time. What is the probability that the sum of both rolls is a prime number less than $6$? 
选项为:A:$\dfrac{7}{36}$.  B:$\dfrac{1}{6}$.  C:$\dfrac{5}{36}$.  D:$\dfrac{1}{9}$.  E:$\dfrac{5}{12}$.  请回答其中一个选项.