I think it is C by POE

A - I see no contradiction between the claim "Recently

someone has in fact proved Fermat's

theorem." and the conclusion "And since the theorem is provable,

your claim-that Fermat was lying or

mistaken-clearly is wrong.".

B - 'Person's character' makes it out of scope

D - 'provable' makes sense with the context

E - I see no 'true claim bla bla' and no 'false claim bla bla'

As for C,

The statement "Recently someone has in fact proved Fermat's

theorem" is necessary for the conlusion but not sufficient enough. That points out the error.

OlegC wrote:

Joseph: My encyclopedia says that the

mathematician Pierre de Fermat died in 1665

without leaving behind any written proof for

a theorem that he claimed nonetheless to

have proved. Probably this alleged theorem

simply cannot be proved, since-as the

article points out-no one else has been able

to prove it. Therefore it is likely that Fermat

was either lying or else mistaken when he

made his claim.

Laura: Your encyclopedia is out of date. Recently

someone has in fact proved Fermat's

theorem. And since the theorem is provable,

your claim-that Fermat was lying or

mistaken-clearly is wrong.

Which one of the following most accurately

describes a reasoning error in Laura's

argument?

(A) It purports to establish its conclusion by

making a claim that, if true, would

actually contradict that conclusion.

(B) It mistakenly assumes that the quality of a

person's character can legitimately be

taken to guarantee the accuracy of the

claims that person has made.

(C) It mistakes something that is necessary

for its conclusion to follow for

something that ensures that the

conclusion follows.

(D) It uses the term "provable" without

defining it.

(E) It fails to distinguish between a true claim

that has mistakenly been believed to be

false and a false claim that has mistakenly

been believed to be true.

_________________

Awaiting response,

Thnx & Rgds,

Chandra