The matrix $A = \begin{bmatrix} 0 & 1 & -3\\ -1 & 0 & 0 \\ 3 & 0 & 0 \end{bmatrix}$ is a

Diagonal matrix Symmetric matrix Skew-symmetric matrix Scalar matrix

Skew-symmetric matrix

$A = \begin{bmatrix} 0 & 1 & -3\\ -1 & 0 & 0 \\ 3 & 0 & 0 \end{bmatrix}$ $A^T = \begin{bmatrix} 0 & -1 & 3\\ 1 & 0 & 0 \\ -3 & 0 & 0 \end{bmatrix}$ $A = -A^T$ ⇒  A is skew symmetric