Answer: The following versions of the underlined portion of senence 14 that best accomplishes this goal is C. a nonpartisan organization known for conducting impartial economic analyses since 1975.
Explanation: Option C best accomplishes the goal of convincing readers to accept the research of the Congressional Budget Office as credible because it emphasizes the impartial and unbiased nature of the organization. By stating that the CBO is a nonpartisan organization known for conducting impartial economic analyses, the writer is highlighting its credibility and reputation, which will help to convince readers to accept its findings. This option is better than option A, which only mentions the CBO's function as an organization that conducts analyses, and option B, which only mentions its history but not its reputation for impartiality.