A fair $6-$sided die is rolled twice. What is the probability that the sum of the two rolls\textquotesingle{} outcomes is a perfect square? 
选项为:A:$\dfrac{1}{27}$  B:$\dfrac{7}{9}$  C:$\dfrac{7}{36}$  D:$\dfrac{1}{9}$  E:$\dfrac{5}{18}$  请回答其中一个选项.