A matrix SSS is symmetric if S=STS = S^TS=ST. Which matrix is symmetric?
(1234)\begin{pmatrix} 1 & 2 \\ 3 & 4 \end{pmatrix}(1324)
(2113)\begin{pmatrix} 2 & 1 \\ 1 & 3 \end{pmatrix}(2113)
(1020)\begin{pmatrix} 1 & 0 \\ 2 & 0 \end{pmatrix}(1200)
(0123)\begin{pmatrix} 0 & 1 \\ 2 & 3 \end{pmatrix}(0213)