From matrices A, B, C, and D, only C and D are square matrices (they have the same number of rows and columns).
To sum these two matrices, we need to add each element of the same position:
[tex]\begin{bmatrix}{-1} & {2} & {5} \\ {0} & {-4} & {1} \\ {-4} & {3} & {1}\end{bmatrix}+\begin{bmatrix}{3} & {6} & {-9} \\ {1} & {4} & {2} \\ {3} & {-5} & {0}\end{bmatrix}=\begin{bmatrix}{-1+3} & {2+6} & {5-9} \\ {0+1} & {-4+4} & {1+2} \\ {-4+3} & {3-5} & {1+0}\end{bmatrix}[/tex]
Finally, the result of the sum is:
[tex]\Rightarrow=\begin{bmatrix}{2} & {8} & {-4} \\ {1} & {0} & {3} \\ {-1} & {-2} & {1}\end{bmatrix}[/tex]
