Which of these is a square matrix?
(1234)\begin{pmatrix} 1 & 2 \\ 3 & 4 \end{pmatrix}(1324)
(123)\begin{pmatrix} 1 & 2 & 3 \end{pmatrix}(123)
(123)\begin{pmatrix} 1 \\ 2 \\ 3 \end{pmatrix}123
(123456)\begin{pmatrix} 1 & 2 \\ 3 & 4 \\ 5 & 6 \end{pmatrix}135246