设 $D$ 是第一象限中曲线 $2 x y=1,4 x y=1$ 与直线 $y=x$ ， $y=\sqrt{3} x$ 围成的平面区域，函数 $f(x, y)$ 在 $D$ 上连续，则 $\iint_D f(x, y) \mathrm{d} x \mathrm{~d} y=$
A. $\int_{\frac{\pi}{4}}^{\frac{\pi}{3}} \mathrm{~d} \theta \int_{\frac{1}{2 \sin 2 \theta}}^{\frac{1}{\sin 2 \theta}} f(r \cos \theta, r \sin \theta) r \mathrm{~d} r$
B. $\int_{\frac{\pi}{4}}^{\frac{\pi}{3}} \mathrm{~d} \theta \int_{\frac{1}{\sqrt{2 \sin 2 \theta}}}^{\frac{1}{\sqrt{\sin 2 \theta}}} f(r \cos \theta, r \sin \theta) r \mathrm{~d} r$
C. $\int_{\frac{\pi}{4}}^{\frac{\pi}{3}} \mathrm{~d} \theta \int_{\frac{1}{2 \sin 2 \theta}}^{\frac{1}{\sin 2 \theta}} f(r \cos \theta, r \sin \theta) \mathrm{d} r$
D. $\int_{\frac{\pi}{4}}^{\frac{\pi}{3}} \mathrm{~d} \theta \int_{\frac{1}{\sqrt{2 \sin 2 \theta}}}^{\frac{1}{\sqrt{\sin 2 \theta}}} f(r \cos \theta, r \sin \theta) \mathrm{d} r$