The question stem reads: The reasoning in the argument is flawed because of the argument… This is a Weaken question.
The author beings with context, saying that Roger Bacon is a 13-century scientist who is said to have made important optics discoveries. They also claim he preached both hands-on experimentation and not uncritically relying on the opinion of authority to his students. However, the author notes that Bacon would appeal to authority when it was expedient (beneficial) for Bacon's argumentation. So Mr. Bacon was a bit of a hypocrite. The author concludes that Bacon's scientific work must be disregarded because of his hypocritical behavior.
Immediately this jumps out as an ad hominem attack, using someone's character instead of their position. In this case, the author claims we should disregard Bacon's work. Why? Because, on the authors' account, Bacon had some unsavory personality traits. When we attack opponents' arguments or work, our argument needs to be directed at that argument or work. In this case, the author has only provided reasons to think Bacon is a hypocrite and no evidence to discredit the validity of Bacon's discoveries. If this were a sufficient assumption question, we would need a premise like Hypocritie -> disregard work on optics, to bridge the gap between Bacon's personality and his work.
Answer Choice (A) is wrong because the author does not presume the authority's opinion is incorrect. If we turn to the stimulus, the author has nothing to say about whether authority opinion is correct or incorrect.
Answer Choice (B) is incorrect because the author does not actually attack the fact that Bacon relied on authority opinion. The author attacks Bacon for saying one thing and doing another. The author might think that relying on authority opinion is an acceptable practice while still taking issue with Bacon's hypocrisy.
Answer Choice (C) is incorrect because the author does not use bacon remarks to his students to make an inference of Bacon's opinions. He uses Bacon's comments to infer that he is a hypocrite.
Answer Choice (D) is incorrect because the argument is based on Bacon's character - not on whether or not thirteenth-century science holds up well today. Additionally, (D) would not be a problem for the argument as it lends some (minor) credence to the conclusion that Bacon's work should be disregarded.
Correct Answer Choice (E) is our prephase. The author criticizes Bacon's character (the hypocrisy) in order to question his scientific findings (his work on optics).
The question stem reads: Which one of the following, if true, most weakens the detective's argument? This is a Weaken question.
The author begins by stating that laser-printed drums can be easily damaged, and a damaged drum will produce a blemish of similar dimension on the documents it prints. The author concludes that if we can match a blemish on the page to a nick on the drum, we can reliably trace suspicious laser-printed documents to the printer on which they were printed. In this question, it is difficult to anticipate where the correct AC will go because this argument does not seem to have a fatal flaw. However, we should be aware of some important elements of the stimulus. First, the conclusion uses the modifier "suspicious," so we are not concerned with any documents, just the suspicious ones. Second, the conclusion does not say we can trace any suspicious document to its printer, just the documents where we can match the blemish to a nick on the drum. Let's proceed to the answer choices and use POE.
Answer Choice (A) is irrelevant to the argument. The argument concludes that we can trace a document to the printer on which it was produced. The argument is unconcerned with who printed the document. If you picked this argument, you likely assumed that the argument's author, a detective, was interested in catching criminals. Perhaps the detective is, but his argument is not. It can be helpful to think of arguments as standing on their own. It does not matter who is making the argument; stick to strictly the premises and conclusions of the argument.
Answer Choice (B) is also irrelevant. The fact that nicks are usually small and require skill to determine size does not imply that we cannot match the blemish to the nick on the drum. Even if it did make it impossible to match the small blemish to the nick, the argument would not be concerned with those documents. Remember, the argument is only concerned with the blemishes we can match.
Correct Answer Choice (C) hurts the argument severely. Let's say the manufacturing process often produces the same nick in three multiple drums. Matching the blemish on a document to that nick would only narrow it down to three printers. That would directly contradict the argument's conclusion, which says we could find the exact printer the document was printed.
Answer Choice (D) is similar to (B). Just because the blemishes are sometimes totally concealed does not necessarily mean we would be unable to find the blemish and match it to the nick. If it were impossible to match a concealed blemish to the drum, then (D) would be irrelevant to the argument. Remember, the arguments are only concerned with documents we are able to match to a drum.
Answer Choice (E) is irrelevant to the argument. The conclusion is concerned only with laser-printed suspicious documents.