Which sentence has a pronoun reference problem?

a- like their counterparts in hamlet, rosencrantz and guildenstern are powerless against their fate.

b- in both plays, rosencrantz and guildenstern feel they must come because they have been summoned by the king.

c- stoppard's title characters pass their time playing word games and pondering their situation instead of taking control of their lives.

tom stoppard tells his version of the story of hamlet's college friends in his play rosencrantz and guildenstern are dead