Which of the following is true of hydrogen peroxide and carbamide peroxide as tooth bleaching agents? a) Carbamide peroxide is three times stronger than hydrogen peroxide and has a shorter working time. b) Hydrogen peroxide is three times stronger than carbamide peroxide and has a longer working time. c) Hydrogen peroxide is three times stronger than carbamide peroxide and has a shorter working time. d) Carbamide peroxide is three times stronger than hydrogen peroxide and has a longer working time.