The potential energy of a particle in a central field has the form $U\left(r\right)=\frac{1}{r^2}-\frac{1}{r},$ where $\text{'}r\text{'}$ is the distance from the centre of the field. The magnitude of the maximum attractive force in Newton is

• Correct answer
  A

  $\frac{1}{27}$
• B

  $\frac{1}{9}$
• C

  $\frac{1}{3}$
• D

  $1$

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