A matrix AAA is skew-symmetric if AT=−AA^T = -AAT=−A. Which of the following is skew-symmetric?
(1223)\begin{pmatrix} 1 & 2 \\ 2 & 3 \end{pmatrix}(1223)
(02−20)\begin{pmatrix} 0 & 2 \\ -2 & 0 \end{pmatrix}(0−220)
(1234)\begin{pmatrix} 1 & 2 \\ 3 & 4 \end{pmatrix}(1324)
(1−220)\begin{pmatrix} 1 & -2 \\ 2 & 0 \end{pmatrix}(12−20)