30. As shown in Figure 2, $C$ is a point on ray $\overrightarrow{A E}$, and $B D$ bisects $\angle A B C$. If $\angle B A E = 30^{\circ}$, then for all possible positions of $B, C$, the range of $\angle C B D$ is ( ).
(A) $0^{\circ}-30^{\circ}$
(B) $0^{\circ}-60^{\circ}$
(C) $0^{\circ} \sim 75^{\circ}$
(D) $0^{\circ} \sim 150^{\circ}$
(E) $0^{\circ} \sim 180^{\circ}$
30. (C).
$$
\begin{array}{l}
\because B D \text { bisects } \angle A B C . \\
\begin{aligned}
\therefore \angle C B D & =\frac{1}{2}\left(180^{\circ}-\angle A-\angle B C A\right) \\
& =\frac{1}{2}\left(150^{\circ}-\angle B C A\right) \leqslant 75^{\circ} .
\end{aligned}
\end{array}
$$

When $B \rightarrow A$, $\angle B C A \rightarrow 0^{\circ}$. At this time, $\angle C B D \rightarrow 75^{\circ}$;
When $C \rightarrow A$, $\angle C B 4 \rightarrow 0^{\circ}$. At this time, $\angle C B D \rightarrow 0^{\circ}$.