I believe the reason why D can still be true because it states "either the economy is weak OR prices are constant."Now, we already know that the economy is not weak based on the stimulus--so we can get rid of that. However, we don't know anything about whether prices are constant. They could very well be constant, in which case, the statement made by AC D is true. Even if just one part of the either/or part can be true, that makes it an incorrect answer for a MBF question.

TLDR, the #2 conditional you wrote out seems to not affect the fact that AC D COULD be true since the #1 conditional still may very well be. At least that's how I'm thinking about it.

I had the same question at first--I think D works because it establishes that the two studies cannot be used to support "ANY conclusion regarding a causal relationship between nightlights and nearsightedness"

The author's conclusion is causal: "IF night-lights cause nearsightedness, the effect disappears with age."--> therefore, if AC D were true, we would not be able to support this conclusion because we only have one remaining study with one age group as our evidence.

@sekim21128 how many times did you score above 170 before taking the actual test?