The DISCUSSION section of scientific journal papers tends to be one of the most mis-understood by students reading these sorts of articles for the first time. It might also surprise you that the DISCUSSION section is also often misunderstood by students trying to work on their first research publication (either as seniors or masters students). What is the DISCUSSION section of this paper (by Sallis and others "co-benefits of designing communities for active living...") trying to achieve?

To link the findings of the research to the prior literature, all while pulling together some main themes of the results

Explanation:

The discussion section of scientific paper must make connections between the results and the prior research literature on the topic, such that the discussion decsribes how the study enhance the reader's understanding of the research problem from where it stopped at the end of the review of prior research.

Hence, in this case, the paper links the findings of the research to the prior literature, all while pulling together some main themes of the results, to advanced the readers' understanding of the research work.

a is the answer because it just is

what is the question?