Answer: quoting.
The best method for incorporating evidence in this case would be quoting. This is because the original text is easily accessible, and because, if the reader were to question your argument, he would be able to easily compare your analysis with the text. Moreover, your claim refers to the use of language in the book, which does not require secondary sources in order to be interpreted.
The best answer for this question would be:
Alvarez grappled with the issue of writing a novel about a dangerous subject.
A central idea focuses on the dominant impression of a story in which a general truth of the story is found within it.
I believe the answer is c also
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