Two satellites of same mass are launched in the same orbit of radius r around the earth so as to rotate opposite to each other. If they collide inelastically and stick together as wreckage, the total energy of the system just after collision is

• A

  $- \frac{2GMm}{r}$

• B

  $- \frac{GMm}{r}$

• C

  $\frac{GMm}{2r}$

• D

  zero