A

$\displaystyle\int_0^{\frac{\pi}{2}}d\theta\int_0^{2\sin\theta}f(r^2)rdr$

B

$\displaystyle\int_0^{\frac{\pi}{2}}d\theta\int_0^{2\cos\theta}f(r^2)rdr$

C

$\displaystyle\int_0^{\pi}d\theta\int_0^{2\sin\theta}f(r^2)rdr$

D

$\displaystyle\int_0^{\pi}d\theta\int_0^{2\cos\theta}f(r^2)rdr$