Option (a) is correct because total charge of the universe is constant. It just gets transferred from one particle to another.

Option (b) is incorrect as the total positive charge of the universe is not constant. It is because the positive charges get converted into negative charges and vice-versa.

Option (c) is incorrect as the total negative charge of the universe is not constant. It is because the negative charges get converted into positive charges and vice-versa.

Option (d) is incorrect as in universe, the total number of charged particles is not a constant as a pair of positive and negative charges appear at the time of pair production and a pair of positive and negative charge combine to form a neutral particle at the time of pair annihilation.