Final answer:
The passage indicating the nun's compassion in 'The Canterbury Tales' is the one where she weeps for a trapped mouse, showing her empathy for creatures.
Step-by-step explanation:
The excerpt from “The Prologue” of The Canterbury Tales that best indicates the nun is a compassionate person is option C: “She used to weep if she but saw a mouse caught in a trap, if it were dead...”. This passage suggests that the nun has a sensitive and sympathetic nature, as she displays empathy towards even the smallest creatures. Her ability to weep for a trapped mouse indicates a gentle character and an innate sense of compassion, traits highly valued in the depicted society and consistent with the ideal of Christian charity.