If $\int \frac{x^4+1}{x^2+1} d x=A x^3+B x^2+C x+D \operatorname{Tan}^{-1} x+E$, then $A+B+C+D=$

• A

  $\frac{3}{2}$
• Correct answer
  B

  $\frac{4}{3}$
• C

  $\frac{1}{3}$
• D

  $\frac{2}{3}$

Hence, the correct answer is option: 'B'.