A student sketches the variation of gravitational force F with distance r for two given masses and notices that the curve approaches but never meets the r-axis. Which statement best explains this observation?
(a) Gravitational force becomes exactly zero at a very large but finite distance.
(b) Beyond a certain distance the outward centrifugal force of motion balances gravity, so the net force becomes zero.
(c) Gravitational force varies as 1/r2, so it keeps decreasing and approaches but never actually reaches zero.
(d) Because gravitational potential is zero at infinity, the force also becomes zero there, so the curve would meet the axis only at infinity.