Row echelon form

Choose matrices in echelon form:

$A=\begin{pmatrix} 2 & 8 & 4 & 0\\ 0 & 5 & 0 & 0\\ 0 & 0 & 2 & 8\\ 0 & 0 & 0 & 0\\ \end{pmatrix}$ $B=\begin{pmatrix} 1 & 0 & 0 & 0\\ 0 & 2 & 5 & 6\\ 0 & 8 & 4 & 5\\ 0 & 0 & 0 & 1\\ \end{pmatrix}$ $C=\begin{pmatrix} 0 & 0 & 0 & 1 & 1\\ 0 & 0 & 0 & 0 & 0\\ \end{pmatrix}$ $D=\begin{pmatrix} 2 & 0 & 8 & 4 & 5\\ 0 & 0 & 3 & -2 & 1\\ 0 & 0 & 0 & 0 & 0\\ 0 & 0 & 0 & 1 & 2\\ 0 & 0 & 0 & 0 & 8\\ \end{pmatrix}$