If S is the set of distinct values of ‘b’ for which the following system of linear equations$x+y+z=1 \\ x+ay+z=1 \\ ax+by+z=0 $ has no solution, then S is :

Question

$\begin{array}{1 1} \text{(1) an infinite set} \\ \text{(2) a finite set containing two or more elements} \\ \text{(3) a singleton} \\ \text{(4) an empty set} \end{array} $