What is $\lim _{x \rightarrow \infty}\left(\sqrt{a^2 x^2+a x+1}-\sqrt{a^2 x^2+1}\right)$ equal to?

• Correct answer
  A

  $\frac{1}{2}$
• B

  1
• C

  2
• D

  0

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