Suppose that the equations $x ^ { 2 } + b x + c a = 0$ and $x ^ { 2 } + c x + a b = 0$ have exactly one common non-zero root. Then\\
(A) $a + b + c = 0$.\\
(B) the two roots which are not common must necessarily be real.\\
(C) the two roots which are not common may not be real.\\
(D) the two roots which are not common are either both real or both not real.