Fill in the Blank Using Elementary Row Operations to Form

Multiple Choice

Fill in the blank using elementary row operations to form a row-equivalent matrix.
$$\begin{array} { l } { \left[ \begin{array} { c c c } 2 & - 1 & - 9 \\8 & - 6 & 4\end{array} \right] } \\{ \left[ \begin{array} { c c c } 2 & - 1 & - 9 \\0 & \square & 40\end{array} \right] }\end{array}$$

A) $\left[ \begin{array} { r r r } 2 & - 1 & - 9 \\ 0 & - 2 & 40 \end{array} \right]$
B) $\left[ \begin{array} { c c c } 2 & - 1 & - 9 \\ 0 & 0 & 40 \end{array} \right]$
C) $\left[ \begin{array} { c c c } 2 & - 1 & - 9 \\ 0 & - 10 & 40 \end{array} \right]$
D) $\left[ \begin{array} { c c c } 2 & - 1 & - 9 \\ 0 & - 1 & 40 \end{array} \right]$
E) $\left[ \begin{array} { c c c } 2 & - 1 & - 9 \\ 0 & 2 & 40 \end{array} \right]$