The system of equations <br>$\alpha x + y + z = \alpha -1$<br>$x + \alpha y + z = \alpha -1$ <br>$x + y + \alpha z = \alpha - 1$ <br> has no solution, if $\alpha$ is :

Question

( A ) either -2 or 1
( B ) 1
( C ) not -2
( D ) -2