Thanks for the question! I’d categorize this as a “methods of reasoning” question; you can tell that because it asks you how the argument proceeds—or in other words, the method by which the reasoning is conducted. So we’re looking for an answer choice that shows the evidence that the argument presents. And here, it’s going to be (D), that failure to enact the ban would have unacceptable risks (poison fish) for the public welfare. The argument presents evidence for this when it talks about the recent study.
Hope this helps! Feel free to ask any other questions that you might have.