The distance between the parallel lines $9 x^2-6 x y+y^2+18 x-6 y+8=0$ is

• A

  $\sqrt{10}$
• B

  2
• C

  $\frac{2 \sqrt{153}}{\sqrt{10}}$
• Correct answer
  D

  $\frac{2}{\sqrt{10}}$

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