Student Advisor: One of our exchange students faced multiple

[Gia]

Hi everyone,

Here is a problem on P129, Assumption chapter, Manhattan Critical Reasoning 5th.
----Question No.5 Exchange student
Student Advisor: One of our exchange students faced multiple arguments with her parents over the course of the past year. Not surprisingly, her grade point average (GPA)over the same period showed a steep decline. This is just one example of a general truth: problematic family relationships can cause significant academic difficulties for our students.

The claim by the Student Advisor would be more properly drawn id which of the following were inserted into the argument as an additional premise?
(A) Last year, the exchange student reduced the amount of time spent on academic work, resulting in a lower GPA.
(B) The decline in the GPA of the. exchange student was not the reason for the student's arguments with her parents.
(C) School GPA is an accurate measure of a student's intellectual ability.
(D) If proper measures are not taken, the decline in the student's academic performance may become irreversible.
(E) Fluctuations in academic performance are typical for many students.




correct answer is B, because of the reverse logic.

I am wondering why (C) is not correct.
In this case, one of my brainstormed assuption is that "GPA can be the indicator for acedemic ability, which is the intellectual ability (is it right?)." So, when it comes to (C), it meets the assumption that GPA is the accurate measure of intellectual ability. Here, we can use the negation method. Then (C)'s negation is "GPA is not the accurate measure of intellectual ability", and that clearly hurts the conclusion based on the above assumption. If GPA cannot reflect the academic ability, how can they say the lower GPA means academic difficulties? -----even stronger than (B)

While the MGMAT explains on the accuracy of GPA and i get that point. But my understanding is that the main point is not accuracy but measurement. And in real life the GPA certainly reflect the academic ability, but one of the priciple to do GMAT is "never think about real life".

Is there anything wrong above? Thanks a lot for further explanation:)

[RonPurewal]

"intellectual ability" is very clearly not the same thing as school/academic performance. (this should be clear for lots and lots and lots of reasons -- but, as one principal reason, academic performance depends on doing things like homework, while "intellectual ability" most certainly does not.)

thus C is irrelevant.

[Gia]

"intellectual ability" is very clearly not the same thing as school/academic performance. (this should be clear for lots and lots and lots of reasons -- but, as one principal reason, academic performance depends on doing things like homework, while "intellectual ability" most certainly does not.)

thus C is irrelevant.

yeah! Thanks Ron! I know more about the tactics for CR now.

[RonPurewal]

excellent.