Answer
B is the inverse of A
Work Step by Step
When there is an inverse of a matrix $A A^{-1} = I$ (the Identity Matrix)
$AB = \begin{bmatrix} -4 & 1 & 5 \\-1 & 2 & 4 \\ 0 &-1 & -1 \end{bmatrix} \dfrac{1}{4}\begin{bmatrix} -2 & 4 & 6 \\1 & -4 & -11 \\ -1 & 4 & 7 \end{bmatrix} =\begin{bmatrix} 1 & 0 &0\\ 0 & 1 &0 \\0 &0&1\end{bmatrix}$
and $BA =\dfrac{1}{4}\begin{bmatrix} -2 & 4 & 6 \\1 & -4 & -11 \\ -1 & 4 & 7 \end{bmatrix} \begin{bmatrix} -4 & 1 & 5 \\-1 & 2 & 4 \\ 0 &-1 & -1 \end{bmatrix} =\begin{bmatrix} 1 & 0 &0\\ 0 & 1 &0 \\0 &0&1\end{bmatrix}$
Since $AB=BA$ equals the identity matrix, B is the inverse of A.
