In a cosmic event, suppose a planet heavier than the earth with mass KM (K > 1) and radius K'R (K' > 1) passes through a path near the earth (M and R are the mass and radius of earth).At what closest distance from surface of planet, we are in danger of being thrown into space:

• A

  ${\left[\frac{2\mathrm{KGM}}{\mathrm{g}}\right]}^{1/2}-\frac{1}{2}{\mathrm{K}}^{\mathrm{\prime }}\mathrm{R}$

• B

  ${\left[\frac{\mathrm{KGM}}{2\mathrm{g}}\right]}^{1/2}-\frac{1}{2}{\mathrm{K}}^{\mathrm{\prime }}\mathrm{R}$

• C

  ${\left[\frac{\mathrm{KGM}}{\mathrm{g}}\right]}^{1/2}-\frac{1}{2}{\mathrm{K}}^{\mathrm{\prime }}\mathrm{R}$

• D

  ${\left[\frac{\mathrm{KGM}}{\mathrm{g}}\right]}^{1/2}-{\mathrm{K}}^{\mathrm{\prime }}\mathrm{R}$