Determine whether the following matrices are in echelon form, reduced echelon form or not in echelon form.

1. Choose Echelon Form Reduced Echelon Form Not in Echelon Form $\left[\begin{array}{cccc} 1 &0 &0 &9\cr 0 &1 &0 &-9\cr 0 &0 &0 &0 \end{array}\right]$
   
   
2. Choose Echelon Form Reduced Echelon Form Not in Echelon Form $\left[\begin{array}{ccc} -9 &0 &1\cr 0 &-3 &0 \end{array}\right]$
   
   
3. Choose Echelon Form Reduced Echelon Form Not in Echelon Form $\left[\begin{array}{cccc} 1 &0 &0 &8\cr 0 &0 &0 &0\cr 0 &1 &0 &7 \end{array}\right]$
   
   
4. Choose Echelon Form Reduced Echelon Form Not in Echelon Form $\left[\begin{array}{ccc} 1 &0 &0\cr 0 &1 &0\cr 0 &0 &0 \end{array}\right]$