Three small pieces of electrically neutral paper are placed far apart from one another on a table. One piece is given a negative electric charge, one is given a positive charge, and one is left neutral. They all look identical, and in order to tell which is which, a student runs a comb through her hair and waves the comb over each piece. She observes that one is strongly attracted to the comb; she labels this A. She observes that another is weakly attracted to the comb; she labels this \(\mathrm{B}\). The last piece, which is repelled by the comb; she labels \(\mathrm{C}\). Which piece is positive, which is negative, and which is neutral?