设平面区域$D=\left\{ (x,y)\left| 0\le x\le 1,0\le y\le 1 \right. \right\}$,则二重积分 $\iint\limits {D}{\frac{y}{{{(1+{{x}^{2}}+{{y}^{2}})}^{\frac{3}{2}}}\text{d}x\text{d}y}=$ ( ).A.$\ln \frac{2-\sqrt{2}}{\sqrt{3}+1}$B.$\ln...