$\int \frac{x^4-1}{x^2 \sqrt{x^4+x^2+1}} d x=$

• A

  $\frac{2 \sqrt{x^4+x^2+1}}{x}+c$
• Correct answer
  B

  $\frac{\sqrt{x^4+x^2+1}}{x}+c$
• C

  $\frac{\sqrt{x^4+x^2+1}}{2 x}+c$
• D

  $\frac{4 \sqrt{x^4+x^2+1}}{x}+c$

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