This is an opinion thing. There is no right or wrong so not a good question to ask help on.
A man has a dream could be foreshadowing, depending on what the man dreams about. If the narrator is not a character in the story, but just telling the story, seeing a ship and seeing a white flag could be foreshadowing.<span />
I would say C is the best answer. The students didn't know the customs because they weren't taught them, and the story is clearly conveying that it was a mistake that wasn't their fault.
