If $3 \sqrt{2} x-4 y=12$ is a tangent to the hyperbola $\frac{x^2}{a^2}-\frac{y^2}{b^2}=1$ and $\frac{5}{4}$ is its eccentricity, then $a^2-b^2=$

• A

  $5$
• Correct answer
  B

  $7$
• C

  $9$
• D

  $11$

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