# The inverse of the matrix $\begin{bmatrix} 2 & 1 \\ 1 & 3 \end{bmatrix}$ is :
( A ) $\frac{2}{5}\begin{bmatrix} -3 & 1 \\ 1 & 2 \end{bmatrix}$
( B ) $\frac{1}{5}\begin{bmatrix} 3 & -1 \\ -1 & 2 \end{bmatrix}$
( C ) $\frac{1}{5}\begin{bmatrix} -3 & 1 \\ 1 & 2 \end{bmatrix}$
( D ) $\frac{1}{5}\begin{bmatrix} 2 & 1 \\ 1 & 3 \end{bmatrix}$