Can somebody please be so kind as to explain me why the ans is E and not D (example comes from Kaplan
's GMAT 800
- but I still don't get the explanation).
Reading skills among high school students in Gotham have been steadily declining, which can only be the result of overcrowding in the schools.
Which of the following, if true, most seriously weakens the argument above?
A. The high school system in Gotham succeeds in giving students a good education at considerably less cost than do most systems.
B. Several cities have found that overcrowding in the schools is not always associated with lower reading scores.
C. Gotham schools have a greater teacher-to-student ratio than most other school systems.
D. Students' reading skills have not declined in other cities where the high schools are just as overcrowded as those of Gotham.
E. Schools are not overcrowded in many cities where high school reading scores have declined more than they have in Gotham.
Why E??? For me it's clearly D because:
1) it offers alternative explanation (there must be some other reason for decline in reading skills than overcrowded schools)
2) E talks about "scores" not "skills" - isn't it a shift of scope?
It is possible that the schools in Gotham have now become equally overcrowded as the schools in other cities while that was not the case before. Where as the schools in the other cities have not seen any increase in the overcrowding and hence the students' reading skills have not declined.
Reading Skill for Gotham City Students = 87, Reading Skill for Other city students = 75
Gotham City overcrowding ratio = 0.99, Other Cities overcrowding ratio = 0.99 (unchanged)
Reading Skill for Gotham City Students = 75, Reading Skill for Other city students = 75
So just the fact that the students of other cities have not seen any declines in reading skills (even though the crowding ratio is equal) is not enough to weaken the argument.