Which of the following is true for center of mass ? (i) The center of mass of a body may lie within , outside , on the surface of the body. (ii) In the case of symmetrical bodies , the center of mass coincides with the geometrical center of the body. (iii) In the absence of external forces , the center of mass moves with constant velocity. (iv) If external forces are absent and system is initially at rest, then location of center of mass is fixed.