8. As shown in the figure, in $\triangle ABC$, $D$ is the midpoint of $AB$. Fold $\triangle ACD$ along line $CD$ to form $\triangle A'CD$. The dihedral angle $A' - CD - B$ has plane angle $\alpha$. Then\\
A. $\angle A' D B \leq \alpha$\\
B. $\angle A' D B \geq \alpha$\\
C. $\angle A' C B \leq \alpha$\\
D. $\angle A' C B \geq \alpha$

II. Fill-in-the-Blank Questions: This section contains 7 questions. Multi-blank questions are worth 6 points each, single-blank questions are worth 4 points each, for a total of

\begin{figure}[h]
\begin{center}
  \includegraphics[alt={},max width=\textwidth]{dc06d11b-7713-423c-95b9-1351bb88518a-1_303_270_2224_1391}
\captionsetup{labelformat=empty}
\caption{36 points.}
\end{center}
\end{figure}