For the past two decades, Eton Coaching Institute has been the market

(A) There is something unique about the books provided by the Eton Coaching Institute that makes its students perform very well in the medical school entrance test. - out of scope as nothing about books is mentioned in the prompt
(B) If a student does not join the Eton Coaching Institute, he will most likely fail to clear the medical school entrance test.
- best chances are with Eton but other coaching institutes are also doing well
(C) The teachers at Eton Coaching Institute are probably better than those at other institutes.
out of scope - nothing mentioned about teachers
(D) A student could clear the medical school entrance test, even if he hasn’t prepared with the Eton Coaching Institute.
correct answer - this is true as other institutes are also doing well so a student could clear without eton
(E) If a student has prepared with the Eton Coaching Institute, he will clear the medical school entrance test
- best chances are with eton but not 100% sure

D.
Chances are good with eton classes but new players are also doing well so even without joining eton classes, students can crack exam.

Posted from my mobile device

Hi Ishan,

Let me try to articulate this.

Let's look at and interpret the two sentences:
1- For the past two decades, Eton Coaching Institute has been the market leader in preparing students for the entrance test to medical schools in the country.

Eton has led the market in Medical school entry test preparation. Presumably the market contains other medical school prep companies otherwise Eton would have the market to itself.

2- While several new players have set up shop in the last few years, and have shown good results, it remains without doubts that if a student wishes to ace the medical school entrance test, his best chances are with Eton Coaching Institute.

Sentence 2 validates the presumption- several players are in the market. Sentence 2 tells us that the BEST chances of a student acing their med-entry test are by taking up Eton.

Lets look at the answer choices now
Firstly, an assertion is a factful statement. To assert is to state positively/ forcefully. To assert in the GMAT context is to reinforce/logically and factually conclude.
The statements above, if true, best support which of the following assertions?
(A) There is something unique about the books provided by the Eton Coaching Institute that makes its students perform very well in the medical school entrance test.
There is absolutely no mention of books anywhere. For all we know, Eton could deliver its prep through on-demand platforms or in-person coaching. A is incorrect.

(B) If a student does not join the Eton Coaching Institute, he will most likely fail to clear the medical school entrance test.
This almost taking the logical opposite of the facts we are given. Also, this statement is so absolute that it leaves no room for interpretation. It's basically saying, if x doesn't happen, y won't happen. We cannot deduce this from the factset given. B is incorrect.

(C) The teachers at Eton Coaching Institute are probably better than those at other institutes.
Again, we cannot deduce this based on the facts. What if, Eton Coaching delivers its coaching through videos, books, or other methods?

(D) A student could clear the medical school entrance test, even if he hasn’t prepared with the Eton Coaching Institute.
D CAN be supported. Pay attention to the less absolute 'could' here.

What do we know?
A- Eton is a market leader among at least 2 other market players.
B- The BEST chances of someone acing their test is with ETON

What else does this tell us?
A- Eton is not the ONLY test prep provider
B- The BEST chances, not the ONLY chances, of someone acing their test are with Eton.
Thus, it may be logically supported that A student COULD clear the test, even if he hasn't prepared with Eton

(E) If a student has prepared with the Eton Coaching Institute, he will clear the medical school entrance test.
E is wrong because we are only told that a student has the BEST chances, not GUARANTEED chance.

Best = greater than the rest
Guaranteed chance = 100% certainty

Hope that helps

Official Explanation

Answer: D

Since this is an Inference Question, we need to go through each option one by one.

(A) Not necessarily. The books provided by Eton could very well be the same as those provided by other institutes; maybe it’s the teachers at Eton who are unique.

(B) Extreme inference. The argument never states anything about the chances of a student clearing the medical entrance test. Maybe for other institutes the chances are 2% and for Eton the chances are 10% but even then 90 out of 100 students enrolled at Eton (and 98 of the 100 enrolled at other institutes) will not clear the test.

(C) This is the opposite of A. It could very well be that the books at Eton are better and the teachers are not.

(D) The correct answer. The argument never states that a students’ only chance of clearing the test is with Eton but that his best chances are with Eton. It is very much possible that a student enrols with some other institute (or doesn’t enrol at all) and yet manages to clear the test.

(E) Same as B.