is this for a book and if so what book?
The answer is C. "the man's behavour led me to guess...upset in someone."
Sentences A and B describe the actions and manners, showing the man's behaviour and anxiety: casting quick glances, his foot beating on the hot pavement etc. appearing he could even explode with anger. At some point (C), <em>he changed and just got calm, wainting silently, leading the speaker to wonder if the cause of all this could be the bus' delay.</em>