(A) : Position of centre of mass of a body (w.r.t body frame) is independent of co-ordinate system.
(R ) : Internal forces do not effect the motion of centre of mass.

Options

A. Both (A) and (R ) are true and (R ) is the correct explanation of (A)
B. Both (A) and (R ) are true and (R ) is not the correct explanation of (A)
C. (A) is true but (R ) is false
D. Both (A) and (R ) are false

Answer

B