Hệ phương trình \(\left\{ \begin{array}{l}x - y = 9\\x.y = 90\end{array} \right.\) có nghiệm là:

A. \(\left( {15;6} \right),\left( {6;15} \right).\)

B. \(\left( {--15;--6} \right),\left( {--6;--15} \right).\)

C. \(\left( {15;{\rm{ }}6} \right),\left( {--6;--15} \right).\)

D. \(\left( {15;6} \right),\left( {6;15} \right),\left( {--15;--6} \right),\left( {--6;--15} \right).\)