方程1990x-1989y=1991的一组正整数解是（    ）

A：$\left\{\begin{array}{c}x=12785\\ y=12768\end{array}\right.$

B：$\left\{\begin{array}{c}x=11936\\ y=11941\end{array}\right.$

C：$\left\{\begin{array}{c}x=12785\\ y=12770\end{array}\right.$

D：$\left\{\begin{array}{c}x=13827\\ y=12632\end{array}\right.$