Solve the System by the Substitution Method $$\left\{ \begin{array} { r r } 9 x + y = & 0 \\- 9 x + y = & - 18\end{array} \right.$$

Multiple Choice

Solve the system by the substitution method.
- $$\left\{ \begin{array} { r r } 9 x + y = & 0 \\- 9 x + y = & - 18\end{array} \right.$$

A) $\varnothing$
B) $\{ ( 1 , - 9 ) \}$
C) $\{ ( x , y ) \mid 9 x + y = 0 \}$
D) $\{ ( - 1,9 ) \}$