The interaction energy of London forces between two particles is proportional to ${\mathrm{r}}^x$, where $\mathrm{r}$ is the distance between the particles. The value of $\mathrm{x}$ is :

• A

  $6$
• Correct answer
  B

  $-6$
• C

  $3$
• D

  $-3$

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