D weakens by stating that crowding can not be a deciding factor behind students' reading skills, the reason is something else.

What is the OA?

Thanks.

(D) Students' reading skills have not declined in other cities where the high schools are just as crowded 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 is E better than D?

From option E, how can we deduce that reading scores are not declining because of overcrowding?
Okay, its possible that other schools may have different reasons for declining reading scores but that doesn't mean overcrowding can't be one of the reasons for declining scores.

On the contrary, option D, more directly indicates that overcrowding may not be a reason for declining scores.

I posted an explanation here:

https://www.beatthegmat.com/declining-re ... 81954.html

To weaken , we need to prove that overcrowding is not the only reason for the decline in reading skills.
i was stuck between D and E

D.
it says, there are other cities which are crowded as Gotham, where the reading skills have not declined. So crowing is not the reason

E.
says in some less crowded places, the reading skills declined. So this says that overcrowding is not the only reason. This weakens the argument by elimination overcrowding as a factor for decline i.e some other reason must be there for decline

Hence i feel E is correct

apex231 wrote: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 expressed 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 crowded 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.

OA E

here only is a key word.
overcrowding in schools is a necessary condition.
declining of reading skills is its effect.

if a necessary condition doesn't happen, then its effect will not happen.
But the choice E says necessary condition doesn't happen but its effect happened.
Hence it weakens the argument.

if a necessary condition happens, then its effect may or may not happen.
That's why D is wrong, since it is neither strengthening nor weakening the argument.

It is difficult to understand the concept with this example.
I will try to give a simple example.

Stmt: Given a figure,it can be called square, only if it is a rectangle.
here being a rectangle is a necessary condition for being square.
In addition to it, it can have multiple necessary conditions like...it should have all sides equal, all angles 90 degrees etc etc.,

So based on argument, if I say something is rectangle, then it doesn't mean it is a square.
But if we say it is not rectangle, it is not square for sure.

Hope I made some sense

user123321

I chose E and thank Nice explanation from Mitch.