5. Given $a \neq 0$. The necessary and sufficient condition for the graph of the function $f(x)=a x^{3}+b x^{2}+c x +d$ to be symmetric with respect to the origin is ( ).
(A) $b=0$
(B) $c=0$
(C) $d=0$
(D) $b=d=0$
5.D.

It is known that $f(x)$ is an odd function, so $b=d=0$.