1973 AMC 12 Question 10 - thichhoctoan.com

Question 10

If $n$ is a real number, then the simultaneous system $$
\begin{cases} nx+y=1,\\ ny+z=1,\\ x+nz=1 \end{cases}
$$ has no solution if and only if $n$ is equal to

$-1$
$0$
$1$
$0$ or $1$
$\frac12$