Identify the Indicated Submatrix $A = \left[ \begin{array} { r r | r } 2 & 6 & 1 \\ - 2 & 0 & - 1 \\ 0 & 3 & - 6 \\ \hline 3 & 6 & 3 \end{array} \right] .$

Multiple Choice

Identify the indicated submatrix.
- $A = \left[ \begin{array} { r r | r } 2 & 6 & 1 \\ - 2 & 0 & - 1 \\ 0 & 3 & - 6 \\ \hline 3 & 6 & 3 \end{array} \right] .$

A) $[ 6 ]$
B) $\left[ \begin{array} { l l } 3 & 6 \end{array} \right]$
C) $[ - 2 ]$
D) $\left[ \begin{array} { r } 1 \\ - 1 \\ - 6 \end{array} \right]$