5. $p^{2} \geqslant 4 q$ is ( ) for the real-coefficient equation $x^{4}+p x^{2}+q=0$ to have real roots.
(A) A necessary condition but not a sufficient condition.
(B) A sufficient condition but not a necessary condition.
(C) A necessary and sufficient condition.
(D) Neither a sufficient condition nor a necessary condition.
$\begin{array}{r}5 \\ \mathrm{~A}\end{array}$