PrepTest 159, Section 1, Question 21

What we’re looking for

Working the answers

• A

  Interest in Mercado's work isn't the same as finding this lecture fascinating. Students who couldn't attend don't tell us how the students who did find it fascinating experienced the lecture. A doesn't challenge the inference about that group.

• B

  The rule concerns O'Brien's students. People outside that group can hear the lecture from the beginning and find it dull without contradicting anything the professor says. Their reaction doesn't show what may have happened to the fascinated students in the argument.

• C

  Late students who were not fascinated don't expose the error. We need to consider students who were fascinated despite arriving late. C describes a different group and leaves open the professor's claim about the fascinated students.

• D
  Correct

  This is a roundabout way to describe the possibility we wanted. Break it apart: no O'Brien student belongs to the group that both heard the beginning and found the lecture fascinating.

  Now apply the first premise. Any O'Brien student who heard the beginning would have found it fascinating. Such a student would have to belong to that combined group—but D says no O'Brien student does. So, under this possibility, none of O'Brien's students heard the beginning.

  We still know some of those students found the lecture fascinating. They must have done so without hearing it from the start, just as we predicted. Both premises can hold while the professor's conclusion is false.

• E

  Hearing the entire lecture is different from hearing it from the beginning. A person could hear the opening and then miss a later part because of disruptions. The professor's rule doesn't require uninterrupted attendance for the whole lecture, so this possibility doesn't address the mistaken inference.