If $\frac{3 x+1}{(x-1)^2\left(x^2+1\right)}=\frac{\mathrm{A}}{x-1}+\frac{\mathrm{B}}{(x-1)^2}+\frac{\mathrm{C} x+\mathrm{D}}{x^2+1}$, then $2(\mathrm{~A}-\mathrm{C}+\mathrm{B}+\mathrm{D})=$

• A

  0
• B

  1
• C

  2
• Correct answer
  D

  -1

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