How is a the right answer? It undermines the validity of the study the author's conclusion is based on, by saying the experiments methods weren't reliable, therefore weakening the argument put forth on basis of the study findings. Answer B does nothing to weaken the argument, being tested in their natural settings is irrelevant and this is a weaken except question, so how does weakening the authors conclusion by calling into question the studies methods used to yield the results upon which the conclusion is based not weaken it. That's absurd unless I'm reading it wrong, I may be cuz I'm tired, but I mean how does undermining the validity of the study used to advance the conclusion not weaken the authors argument...?

Yah like answer b does nothing to weaken the argument whereas a clearly calls into question the ability of the experiments chemical smell instruments to successfully emit recognizable smells, thus undermining the validity of the studies findings and subsequently the conclusion drawn by the author thereof. B doesn't weaken whatsoever. If we pay for these services us users expect administrators to at least have the correct answered logged in, things like this can seriously throw someone studying for the test off if they believed the apps correct answer was the actually correct answer. For the exorbitant price of this apps purchases how the hell does something like this happen, if I find too many more of these I'm taking my business to other apps

And I mean instruments in the experimental sense as in the chemicals were instruments involved in carrying out the experiment, just to clarify