The faces of two identical fair dice are numbered $1$, $2$, $3$, $5$, $7$, and $8$. When the two dice are tossed, what is the probability that their sum will be an even number? 
选项为:A:$\dfrac{4}{9}$  B:$\dfrac{1}{2}$  C:$\dfrac{5}{9}$  D:$\dfrac{3}{5}$  E:$\dfrac{2}{3}$  请回答其中一个选项.