After reading the article by The Onion, we can say the impact of the author's diction is the following:
D. This word choice adds to the passage's horrified tone, conjuring similar accounts of human casualties and juxtaposing them to natural selection, thus contributing to the satire of the article.
Diction can be defined as the writing style of an author, determined by his choice of words. Diction can help determine other aspects of the text.
In this case, diction helps determine that the text is a satire. The use of the words "massacred" and "slaughter" while referring to natural selection establishes humor and sarcasm of the text.
The author's purpose is to characterize natural selection as a violent animal, as if it were responsible for mindlessly killing organisms.
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