If the perpendicular drawn from the point $(2,-3)$ to the straight line $4 x-3 y+8=0$ meets it at $\mathrm{M}(a, b)$ and $a^3-b^3=\mathrm{k}^3$, then $\mathrm{k}=$

• A

  1
• B

  -1
• C

  2
• Correct answer
  D

  -2

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