Two point-like charged objects are released at rest in otherwise empty space. As time goes on, the magnitude of the electrostatic force exerted on each of the objects decreases. Which of the following must be true?
(A) Both particles are negatively charged
(B) Not enough info
(C) The particles may be either both positively charged or both negatively charged
(D) One particle is positively charged and the other is negatively charged
(E) Both particles are positively charged