Whoever murdered Jansen was undoubtedly in Jansen’s office on the day

Nice Question!

I think the PowerScore Complete Explanation that Akela posted certainly explains the question completely.

I'll still add my two cents on (C) and (D).

This is an Assumption question, so we can use the negation technique in our POE.

Let's negate (D)



Tempting eh!? If we negate this one, then that surely seems to wreck our conclusion right?

Well, not necessarily. We want to conclude that Samantha was the killer, but we already know that Samantha would not have left fingerprints or footprints.

So, are we even concerned with fingerprints at this point? As long as they are not Herbert's (because if it was him, his fingerprints would have been found) then we can conclude that the murderer is Samantha - given the information that we have.

So Negating (D), although it looks tempting, does not wreck our conclusion.

Now let's negate (C)



Now this is doing some real damage. Our conclusion relies on the premises that Herbert would have left finger/foot prints, but the prints that were found were not his, so it must have been Samantha.

But this negated answer choice brings in some damaging information. There was someone else at the scene of the crime (Jansen's office)! That wrecks our conclusion, it could have been someone else other than Samantha!

Hope this helps.

EXPLANATION FROM POWER PREP

This stimulus provides something of a murder mystery. Jansen’s murderer was in the victim’s office on the day of the crime, and Samantha and Herbert were both in Jansen’s office on that day. Had Herbert committed the crime, the police would have found his fingerprints or footprints at the scene. Had Samantha committed the crime, she would have avoided leaving behind any fingerprints or footprints. Fingerprints were found at the scene, but there were no footprints. The fingerprints did not belong to Herbert, so it makes sense to conclude that he is not the murderer. Once Herbert has been ruled out as a suspect, however, the writer jumps to the conclusion that Samantha must have been the culprit. This argument has many premises, breaking down as follows:

Premise: Jansen’s murderer was in Jansen’s office the day of the crime.

Premise: Samantha and Herbert were both in Jansen’s office that day.

Premise: If Herbert were the culprit, he would have left prints.

Premise: If Samantha were the culprit, she’d have avoided leaving prints.

Premise: The police found fingerprints, but no footprints.

Premise: The fingerprints were not Herbert’s.

Subsidiary
Conclusion: Therefore, Herbert is not the murderer.

Conclusion: Therefore, Samantha must be the killer.

This conclusion is not fully justified based on the information provided. It is possible that Samantha is the killer, because we only know that she would have avoided leaving prints, so the prints found at the scene could have belonged to her. However, this argument is not air-tight, because only two possible suspects have been identified. Could there have been another culprit entirely? There simply is not enough information to justifiably conclude that Samantha was the only conceivable murderer.

The question stem asks which of the answer choices allows the conclusion in the stimulus to be properly drawn. The correct answer choice will allow the reader to justifiably rule out all other possible suspects.

Answer choice (A): Since Herbert has already been ruled out, this answer choice merely lends support to the assertion that Herbert could not have been the culprit.

Answer choice (B): We were told in the stimulus that the murderer was in Jansen’s office on the day the crime took place, so this answer choice provides no additional relevant information to help justify the conclusion that it must have been Samantha.

Answer choice (C): This is the correct answer choice. If all other possible culprits have been eliminated (since the murderer was in the office that day, and Herbert and Samantha were the only ones in the office on the day of the crime), then we can justifiably conclude that the only remaining possible offender would have been Samantha.

Answer choice (D): The stimulus describes the death as a murder, so we already know that the culprit must have been someone other than Jansen. This answer choice, therefore, offers no relevant information to justify the conclusion about Samantha.

Answer choice (E): If the fingerprints found at the scene did not belong to Samantha, this obviously weakens the conclusion that she was the culprit, so this answer choice does not provide an assumption on which the argument depends.