B. people who have good fortune should not expect it to last forever...
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Answer: Describing Crusoe's self-examination develops the idea of battling one's flaws.
Explanation: In this passage, Defoe manages to reveal bits of Crusoe's history while introducing, at the same time, the character's own sense of moral development. We can infer from the words "what would become of me" that the character feels in a more advance moral place, where he can recognize having learned <em>thankfulness</em> and having acquired the capacity for <em>remorse</em>.