9. (2004 Hunan Province College Entrance Examination for Science, Question 12) Let $f(x)$ and $g(x)$ be odd and even functions defined on $\mathbf{R}$, respectively. When $x<0$, $f(x) \cdot g(x)>0$, and $g(-3)=0$. Then the solution set of the inequality $f(x) \cdot g(x)<0$ is
A. $(-3,0) \cup(3,+\infty)$
B. $(-3,0) \cup(0,3)$
C. $(-\infty,-3) \cup(3,+\infty)$
D. $(-\infty,-3) \cup(0,3)$
9. D Let $F(x)=f(x) \cdot g(x)$, by the problem, $F(x)$ is an odd function, and $x0$,
$$

so when $x0$, $F(x)$ is also an increasing function.
Since $F(-3)=f(-3) \cdot g(-3)=0$,
we have $F(3)=-F(-3)=0$.
The left figure is a graph that meets the conditions. Observing it, we find that the solution set for $f(x) \cdot g(x)<0$ is
$(-\infty,-3) \cup(0,3)$.