Which of the following matrices is in row echelon form?
(123001012)\begin{pmatrix} 1 & 2 & 3 \\ 0 & 0 & 1 \\ 0 & 1 & 2 \end{pmatrix}100201312
(123014002)\begin{pmatrix} 1 & 2 & 3 \\ 0 & 1 & 4 \\ 0 & 0 & 2 \end{pmatrix}100210342
(012134001)\begin{pmatrix} 0 & 1 & 2 \\ 1 & 3 & 4 \\ 0 & 0 & 1 \end{pmatrix}010130241
(120001)\begin{pmatrix} 1 & 2 \\ 0 & 0 \\ 0 & 1 \end{pmatrix}100201