Which matrix is upper triangular?
(123456789)\begin{pmatrix} 1 & 2 & 3 \\ 4 & 5 & 6 \\ 7 & 8 & 9 \end{pmatrix}147258369
(100230456)\begin{pmatrix} 1 & 0 & 0 \\ 2 & 3 & 0 \\ 4 & 5 & 6 \end{pmatrix}124035006
(123045006)\begin{pmatrix} 1 & 2 & 3 \\ 0 & 4 & 5 \\ 0 & 0 & 6 \end{pmatrix}100240356
(003205456)\begin{pmatrix} 0 & 0 & 3 \\ 2 & 0 & 5 \\ 4 & 5 & 6 \end{pmatrix}024005356