Which best describes the organization of sinners into the rings of hell:
a: those sinners who have committed multiple sins are only punished according to their gravest sin
b: the sinners who have committed multiple sins must divide their time between multiple rings of hell
c: the sinner who have committed the least grave sins are punished by being forced to inflict harm upon others
d: the sinners who have committed the gravest sins are sent to the lowest rungs of hell