Final answer:
Option (a) is the best summary, wherein Prospero expects obedience from Caliban, who feels enslaved and regrets aiding Prospero but complies due to fear of magic.
Step-by-step explanation:
The best summary of the excerpt from 'The Tempest' is option (a). In the play, Prospero wants his servant Caliban to obey his commands. Caliban, on the other hand, feels oppressed and mistreated, akin to a slave, by Prospero. Despite harboring regret for having shown Prospero kindness in the past, Caliban is compelled to submit because he fears Prospero's powerful magic. Prospero justifies his harsh treatment by referencing a previous incident where Caliban attempted to violate his daughter, Miranda. Caliban does not deny this accusation but argues his actions were natural. Eventually, Caliban begrudgingly agrees to comply with Prospero's demands due to the threat of magical retribution.