To understand what we need for evaluation, we need to dissect the developer’s claim:
Reminder system leads to weight loss; and
Reminder system is the main factor for the app users.
So, in order to validate it, we need to make sure that this app, and specifically its reminder system, is responsible for the success in weight loss, and not any other factors.
Looking at the options, we can get rid of B because the comparison to other apps is irrelevant; and E because it covers the prolonged effect which is not really dealt with by this argument.
Moving on, options A and C are similar, because both of them are referring to other factors that may lead – or may have led – to the weight loss. And indeed, while they would theoretically weaken the argument and help us in evaluating its futility, their impact is not direct enough; plus, it’s difficult to only choose one of those, and there’s only one possible answer. Eliminate.
Eventually, we are left with D, which evaluates not exactly the weight loss success part, but rather the attribution of this success to the reminder system. It’s in line with the developer’s conclusion and hence looks like our answer.
Therefore, D is the right answer.
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