答案：D
$\begin{array}{rcl}
2AB & = & 3 BC \\
\dfrac{AB}{BC} & = & \dfrac{3}{2} \\
\tan \theta & = & \dfrac{3}{2} \\
\theta & = & 56.309~932~47^\circ \\
& \approx & 56^\circ
\end{array}$
$\begin{array}{rcl}
2AB & = & 3 BC \\
\dfrac{AB}{BC} & = & \dfrac{3}{2} \\
\tan \theta & = & \dfrac{3}{2} \\
\theta & = & 56.309~932~47^\circ \\
& \approx & 56^\circ
\end{array}$
