There is no textual support for the portion of answer choice (D) that says that relief agencies and donors "disagree on the proper response methods." In fact, the final paragraph of the passage does not really talk about relief agencies at all - it talks only about donors and the affected communities. For this reason alone, you can safely eliminate (D).
Answer choice (C) correctly states the purpose or role served by the discussion of donors in the final paragraph: to show that implementing an effective disaster relief program requires donors to adopt a new approach. See lines 45-47, especially ("Though this proposal appears sound, its success depends on how an important constituency, namely donors, will respond.").
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