Let $A$ and $B$ be positive whole numbers. $A$ is a $2$-digit number and $B$ is a $4$-digit number. If $A+B$ and $A^{2}+B^{2}$ are both multiples of $7$, find the largest possible value of $B-A$. 
选项为:A:$$9968$$  B:$$9982$$  C:$$9989$$  D:$$9996$$  E:None of the above  请回答其中一个选项.