If \(P(x)=a x^{2}+b x+c\) and \(Q(x)=-a x^{2}+d x+c\), where \(a c \neq 0 \quad[a, b, c, d\) are all real], then \(P(x) \cdot Q(x)=0\) has
\(\begin{array}{llll}\text { (A) at least two real roots }(B) \text { two real roots } & \text { (C) four real roots } & \text { (D) no real root }\end{array}\)