Hi JulesC,
Question 20 asks you to identify "the author’s specific purpose in detailing typical talk-story forms." In other words, why does the author start talking about talk-story forms at that point in the passage? Look at the paragraph referenced, and you will see that it begins with this topic sentence: "Kingston’s participation in the tradition of talk-story is evidenced in her book China Men, which utilizes forms typical of that genre and common to most oral cultures including..." What follows are examples of how Kingston uses the traditional Chinese talk-story forms. Paraphrasing this sentence, one understands that the author believes Kingston is part of the talk-story tradition, and that this can be shown through the examples of the common oral forms used in her book. That is very close to answer choice B.
Note also that test-makers were careful to specify "specific purpose," hinting that the right answer was not necessarily the main point of the passage as a whole. But even if you were attracted to choice E because it was more general, if you reread the first paragraph you'll see that the critics claim Kingston's work did not arise from a prior tradition, not that it should or shouldn't be viewed as literature.
Remember, first figure out what the question is asking, go back to the text to find clues, then prephrase, THEN look at the answer choices!
Happy studying!