Hi g_lawyered!
I think the first thing that's important to keep in mind is what the question itself is asking: what is
explicitly addressed in the passage? So, we already know we're looking for something pretty easy to answer from reading the passage without much (if any) analysis at all.
When looking at answer choice (A), it definitely seems appealing because of the 'undue weight' mentioned in the passage. But, it's important to remember that we don't know how that weight compares to other types of confession evidence, just that it's more than the author would want in an abstract sense.
Another important distinction to make is that (A) is asking if jurors give the same weight to
confession evidence by a cooperating witness and confession evidence offered by the accused; (A) is not asking if jurors give the same weight to cooperating witness testimony - which may or may not include confession evidence, according to line 10 - and confession evidence offered by the accused. While the latter might be answerable from the passage (as you've discussed a bit in your answer), the former is not. Ultimately, the author is definitely saying that jurors give a lot of weight to defendant's confessions and don't necessarily realize how incentives may affect both defendant's confessions and cooperating witness testimony in general, but, this still doesn't answer the question in (A).
Realistically, we can eliminate (A) with this in mind, but let's keep going to discuss more specifics of your analysis. Though you're correct that the author definitely believes jurors place lots of weight on defendant's confession evidence and do not place enough weight on incentives of cooperating witnesses that may bias their testimony, we still do not have any information on how these weights specifically compare to one another, nor do we have information about the weight of cooperating witness
confession testimony specifically. To put it in different terms, we don't really know anything about the author's opinion on the weights given to different types of confession evidence in a scenario where both cooperating witness confession testimony and defendant confession testimony are elicited.
We do, however, know the answer to (D)! Lines 16-17 offer a simple answer: rarely!
I hope this helps!!
-Kate