$A$ particle of mass $m$ is thrown upwards from the surface of the earth with a velocity $u$. The mass and the radius of the earth are $M$ and $R$, respectively. $G$ is the gravitational constant and $g$ is the acceleration due to gravity on the surface of the earth. The minimum value of $u$ so that the particle does not return back to earth is:

• A
  $(\frac{GM}{R})^{1/2}$
• B
  $(\frac{8GM}{R})^{1/2}$
• C
  $(\frac{2GM}{R})^{1/2}$
• D
  $(\frac{4GM}{R})^{1/2}$