This is an example of foreshadowing. This is when the plot gives you details, so in this case the nightmare, that symbolizes a dreadful event will take place sometime later in the story. Foreshadowing is a technique used to hint at something that will transpire in the story and the foreshadowing nearly always appears at the beginning of the story.
B. The sentence that has an error in usage is the following one: Sometimes being a man simply means helping others bare their difficult burdens. The word "bare" in this sentence should be the word "bear" which means "to help endure or carry."
