/u/Lsatter17 You're very close, but the sky is blue is a premise, not an assumption. An assumption is an unstated premised. It must be "assumed." Hence, it usually if not always fails to appear in the argument itself.
/u/q_c_h, flaw questions do not attack the conclusion. They attack the reasoning. One way of reasoning--for better or worse--to is to make assumptions.
To have the quoted answer is as the right answer, you would need a counterargument, then the main argument would have to dismiss the counterargument based on a premise that had been reasonably assumed in the counterargument.
That would a pretty damn complex structure of argument to squeeze onto the LSAT, and IIRC, I've never seen a stimulus like that.
IF IT EXISTED, it must be something like
Mike says Kim loves dogs (Counter Concl.) because she loves friendly creatures (Counter Prem.). However, I know for a fact that Kim does not love dogs (P). Hence, dogs must not be friendly creatures (C).
If the conclusion comes out of left field, it's because the author has to mistakenly assume the falsity of an assumption within the counter. Hence, the "fails to consider that . . . some of the assumptions . . . may nonetheless be true." However, because an assumption isn't written on the page, it just seems like the author is arguing against a stance that no one has championed.
However, if you look at the counterargument, one assumption that Mike reasonably made is that dogs are a subset within the superset of friendly creatures. Hence, if loves friendly creatures --> loves dogs.
Mike's conclusion is falsified because the author threw in a premise, which must be taken at face value, stating otherwise. Based on that premise, the author argues against the reasonable assumption that Mike made about the relationship between dogs and friendly creatures.
The catch is, even though Kim doesn't love dogs, she could not love them because she is allergic to them. Hence, it is still theoretically possible for dogs to be within the superset of friendly creatures, validating the assumption in the counter argument.
Hence, the author "failed to consider that, even if (Mike's) argument's conclusion (that Kim loves dogs) is false, some of the assumptions (like that dogs are friendly creatures) used (by Mike) to justify (his) conclusion may nonetheless be true."
This still conforms with the principle that flaw questions attack reasoning, because the author's reasoning is to assume the falsity of an assumption based on the falsity of resulting argument.
That would be a pretty mean set of reasoning to follow just to get one point... wouldn't it?