Nguyên hàm $I=\int{{\frac{{x\ln \left( {1+{{x}^{2}}} \right)+{{x}^{3}}}}{{1+{{x}^{2}}}}dx}}$ bằng?
A. $\frac{1}{4}{{\ln }^{2}}(1+{{x}^{2}})+\frac{1}{2}{{x}^{2}}-\ln \left( {1+{{x}^{2}}} \right)+C.$ 
B. $\frac{1}{4}{{\ln }^{2}}(1+{{x}^{2}})+\frac{1}{2}{{x}^{2}}-\frac{1}{2}\ln (1+{{x}^{2}})+C.$
C. $-\frac{1}{4}{{\ln }^{2}}(1+{{x}^{2}})+{{x}^{2}}-\frac{1}{2}\ln \left( {1+{{x}^{2}}} \right)+C.$ 
D. $-\frac{1}{4}{{\ln }^{2}}(1+{{x}^{2}})+\frac{1}{2}{{x}^{2}}-\ln \left( {1+{{x}^{2}}} \right)+C.$

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