#4选择题来源：301-2026
已知有界区域 $\Omega$ 由曲面 $z = \sqrt{4 - x^2 - y^2}$ 与 $z = \sqrt{x^2 + y^2}$ 围成,函数 $f(u)$ 连续,则 $\iiint_{\Omega} f(x^2 + y^2 + z^2) dx dy dz = $ ( )
- A. $\int_{0}^{2\pi} d\theta \int_{0}^{2} dr \int_{r}^{\sqrt{4 - r^2}} f(r^2 + z^2) r dz$
- B. $\int_{0}^{2\pi} d\theta \int_{0}^{\sqrt{2}} dr \int_{0}^{\sqrt{4 - r^2}} f(r^2 + z^2) r dz$
- C. $\int_{0}^{2\pi} d\theta \int_{0}^{\frac{\pi}{4}} d\varphi \int_{0}^{2} f(r^2) r^2 \sin\varphi dr$
- D. $\int_{0}^{2\pi} d\theta \int_{0}^{\frac{\pi}{2}} d\varphi \int_{0}^{2} f(r^2) r^2 \sin\varphi dr$