How many free variables does each augmented matrix have?

1. Choose None One Two Three $\left\lbrack \begin{array}{rrr|r} 1 & 5 & 9 & 9 \\ 0 & 0 & 0 & 0 \end{array} \right\rbrack$
   
   
2. Choose None One Two Three $\left\lbrack \begin{array}{rr|r} 1 & 0 & 3 \\ 0 & 1 & 3 \\ 0 & 0 & 0 \end{array} \right\rbrack$
   
   
3. Choose None One Two Three $\left\lbrack \begin{array}{rr|r} 1 & -3 & 3 \\ 0 & 0 & 0 \\ 0 & 0 & 0 \end{array} \right\rbrack$
   
   
4. Choose None One Two Three $\left\lbrack \begin{array}{rrrr|r} 1 & 0 & 0 & 4 & 9 \\ 0 & 1 & 0 & 0 & -9 \\ 0 & 0 & 0 & 0 & 0 \\ 0 & 0 & 0 & 0 & 0 \end{array} \right\rbrack$