Assertion: When we produce charge `q_1` on a body by rubbing it against another body which gets a charge `q_2`, in the process, then `q_1 + q_2 = 0`.
Reason: Charge on an isolated system remains constant.
Options:
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false and R is also false.