答案：C
設 $\theta$ 為該扇形的圓心角，則可得
設 $\theta$ 為該扇形的圓心角，則可得
$\begin{array}{rcl}
\pi (12)^2 \times \dfrac{\theta}{360^\circ} & = & 48\pi \\
\theta & = & 120^\circ
\end{array}$
所以，該扇形的周界
$\begin{array}{cl}
= & 2\pi (12) \times \dfrac{120^\circ}{360^\circ} + 2(12) \\
= & 49.132~741~23 \\
\approx & 49.1\text{ cm}
\end{array}$
