Q. The set $M =\begin{bmatrix}1 & 0 \\ 0 & 1\end{bmatrix},\begin{bmatrix}1 & 0 \\ 0 & -1\end{bmatrix},\begin{bmatrix}-1 & 0 \\ 0 & 1\end{bmatrix},\begin{bmatrix}-1 & 0 \\ 0 & -1\end{bmatrix}$ under matrix multiplication is

Solution:

Correct answer is (b) a commutative group