Let $L_1$ and $L_2$ be two lines in the 3-dimensional space. The line $L_1$ is defined by the equations $\frac{x-1}{3}=\frac{y-2}{2}=\frac{z-3}{\alpha}$ and the line $L_2$ is defined by the equations $\frac{x+2}{-2}=\frac{y-3}{4 \alpha}=\frac{z+7}{3}$ where $\alpha$ is a nonzero real number. If the lines $L_1$ and $L_2$ are mutually perpendicular, then the value of $\alpha$ is

• Correct answer
  A

  $\frac{6}{11}$
• B

  $\frac{4}{3}$
• C

  $\frac{8}{13}$
• D

  $\frac{3}{7}$

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