$A$ particle is kept on the surface of a uniform sphere of mass $1000 \ kg$ and radius $1 \ m$. The work done per unit mass against the gravitational force between them is $\left[G=6.67 \times 10^{-11} \ N \ m^2 \ kg^{-2}\right]$

• A
  $3.35 \times 10^{-10} \ J \ kg^{-1}$
• B
  $-3.35 \times 10^{-10} \ J \ kg^{-1}$
• C
  $6.67 \times 10^{-8} \ J \ kg^{-1}$
• D
  $-3.35 \times 10^{-8} \ J \ kg^{-1}$