Excellent analysis of the question, which is very tricky. I think the reason why B is correct is that it doesn’t account for the clear decline in cigarette smoking. A good RRE answer will account for both parts of the discrepancy.
Thanks for that analysis @allison.gill.sanford! I think that makes a lot of sense. Do you think it's true that you can "get by" with the older PTs with less stringent logic, and that's why the newer ones feel harder? Excited to review with you!!
Accounts playable is right, most of the causation weaken/strengthening questions that i have come across draw some correlation between two things and then make a casual conclusion that you either need to best weaken or best strengthen.