设 $f(x,y)$ 是连续函数,则 $\int_{\frac{\pi}{6}}^{\frac{\pi}{2}}dx\int_{\sin x}^{1}f(x,y)\,dy=(\ )$
- A. $\int_{\frac{1}{2}}^{1}dy\int_{\frac{\pi}{6}}^{\arcsin y}f(x,y)\,dx$
- B. $\int_{\frac{1}{2}}^{1}dy\int_{\arcsin y}^{\frac{\pi}{2}}f(x,y)\,dx$
- C. $\int_{0}^{\frac{1}{2}}dy\int_{\frac{\pi}{6}}^{\arcsin y}f(x,y)\,dx$
- D. $\int_{0}^{\frac{1}{2}}dy\int_{\arcsin y}^{\frac{\pi}{2}}f(x,y)\,dx$