The correct answer is C. Promptly
Step-by-step explanation:
In the third sentence, the word "punctually" is used to refer to the urgency of a male character for collecting his mail, this explained by the narrator as "he came so punctually" that shows when it was time the man was always there, this idea is contrasted by the fact this man rarely received any important mail "he seldom received anything but a copy of the Bettsbridge Eagle". This implies, the word "punctually" refers to the readiness or promptness of the man to collect the mail and thus, this word means promptly.