The quote that most directly addresses this obsession is: D. "In 2011 alone, Americans spent $10.4 billion on cosmetic surgery." (Paragraph 8)
This quote highlights the significant amount of money spent on cosmetic procedures in the United States, indicating a strong cultural emphasis on physical appearance and the pursuit of youthful ideals.
While the other quotes touch upon related themes, such as the constant exposure to images that reinforce unrealistic beauty standards, the spending statistic in quote D provides a more concrete measure of the extent to which Americans are preoccupied with maintaining youthfulness and conforming to societal expectations of beauty.