1. **State the problem:** We are given four matrices: $A$, $B$, $C$, and $D$. We need to find the sum of the two square matrices among them. 2. **Identify the square matrices:** A square matrix has the same number of rows and columns. - $A$ is 3x2 (not square). - $B$ is 3x2 (not square). - $C$ is 3x3 (square). - $D$ is 3x3 (square). 3. **Sum of square matrices:** The sum of two matrices of the same size is found by adding their corresponding elements: $$ (C + D)_{ij} = C_{ij} + D_{ij} $$ 4. **Calculate the sum $C + D$:** \[ C = \begin{bmatrix}-1 & 2 & 5 \\ 0 & -4 & 1 \\ -4 & 3 & 1\end{bmatrix}, D = \begin{bmatrix}3 & 6 & -9 \\ 1 & 4 & 2 \\ 3 & -5 & 0\end{bmatrix} \] Add element-wise: $$ C + D = \begin{bmatrix} -1 + 3 & 2 + 6 & 5 + (-9) \\ 0 + 1 & -4 + 4 & 1 + 2 \\ -4 + 3 & 3 + (-5) & 1 + 0 \end{bmatrix} = \begin{bmatrix}2 & 8 & -4 \\ 1 & 0 & 3 \\ -1 & -2 & 1\end{bmatrix} $$ 5. **Compare with options:** The resulting matrix matches option C. **Final answer:** $$\begin{bmatrix}2 & 8 & -4 \\ 1 & 0 & 3 \\ -1 & -2 & 1\end{bmatrix}$$