Some 200 world-famous physicists recently attended a conference whose

Let's analyze the sentence:

Some 200 world-famous physicists recently attended a conference whose purpose not only was to consider the prospects for the next 50 years of research in physics but also assessing the accuracy of the predictions made at the last meeting of this type, which took place 50 years earlier.

Not only ... but also ... should follow parallel structure.

Here we have "verb" was after "not only" but after "but also" we have verb-ing. These are not parallel. Apart of the parallelism issue, there are no other errors in this sentence. Here from the meaning we have two actions or ideas consider and assess in parallel. So correct option should have these ideas in same grammatical form.

Let look at options:
(A) not only was to consider the prospects for the next 50 years of research
in physics but also assessing the accuracy of the predictions made at the last
meeting of this type,
As discussed above. Eliminate.
(B) not only was considering the prospects for the next 50 years of research
in physics but also assessing the accuracy of the predictions which were
made at the last meeting of this type and

again "was considering" is a helping verb+main verb therefore before assessing we should have a helping verb to make the structure parallel. Eliminate.

(C) was not only considering the prospects for the next 50 years of research
in physics but also to assess the accuracy of the predictions made at the last
meeting of this type and

Here the main verb considering is illegally made parallel to prepositional phrase "to assess". Eliminate.

(D) was not only to consider the prospects for the next 50 years of research
in physics but also to assess the accuracy of the predictions made at the last
meeting of this type,

Here the parallelism is correct. we have prepositional phrase "to consider..." parallel to prepositional phrase "to assess..". Correct option

(E) was to consider not only the prospects for the next 50 years of research
in physics but also assessing the accuracy of the predictions made at the last
meeting of this type,

Here consider should have been parallel to assess. However the parallelism is between "the prospects" and "assessing the accuracy..". Eliminate

THe correct Idiomatic usage is : Not Only X but also Y

None except (D) maintains the correct Parallelism and Idiomatic usage, hence answer will be (D)
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Some 200 world-famous physicists recently attended a conference whose purpose not only was to consider the prospects for the next 50 years of research in physics but also assessing the accuracy of the predictions made at the last meeting of this type, which took place 50 years earlier.

Issues tested: Idiom | Parallelism

Analysis:
1. Looking at the options you will notice idiom "not only... but also....", so the clauses need to be parallel.
2. "whose purpose" should be followed by infinitive and not a gerund here. Consider this example where the conference had only 1 purpose:
-- Right: X recently attended a conference whose purpose was to consider...
-- Wrong: X recently attended a conference whose purpose was considering...

Keeping this in mind, I have highlighted the parallelism issues in the options below:

(A) not only was to consider the prospects for the next 50 years of research in physics but also assessing the accuracy of the predictions made at the last meeting of this type,

(B) not only was considering the prospects for the next 50 years of research in physics but also assessing the accuracy of the predictions which were made at the last meeting of this type and

(C) was not only considering the prospects for the next 50 years of research in physics but also to assess the accuracy of the predictions made at the last meeting of this type and

(D) was not only to consider the prospects for the next 50 years of research in physics but also to assess the accuracy of the predictions made at the last meeting of this type,

(E) was to consider not only the prospects for the next 50 years of research in physics but also assessing the accuracy of the predictions made at the last meeting of this type,

Only option "D" correctly uses correct parallel structure- here we have the idiom "not only..but also" - therefore there needs to be an auxiliary verb accompanying both "asses" and "consider"

Thus
"D"

Some 200 world-famous physicists recently attended a conference whose purpose not only was to consider the prospects for the next 50 years of research in physics but also assessing the accuracy of the predictions made at the last meeting of this type, which took place 50 years earlier.

(A) not only was to consider the prospects for the next 50 years of research in physics but also assessing the accuracy of the predictions made at the last meeting of this type, ---- not only verb….but also present participle is not ok.

(B) not only was considering the prospects for the next 50 years of research in physics but also assessing the accuracy of the predictions which were made at the last meeting of this type and ---- not only verb….but also present participle is not ok.

(C) was not only considering the prospects for the next 50 years of research in physics but also to assess the accuracy of the predictions made at the last meeting of this type and ---- ---- not only present participle ….but also infinitive is not ok.

(D) was not only to consider the prospects for the next 50 years of research in physics but also to assess the accuracy of the predictions made at the last meeting of this type, ---- not only infinitive ….but also infinitive is ok.

(E) was to consider not only the prospects for the next 50 years of research in physics but also assessing the accuracy of the predictions made at the last meeting of this type, ---- not only noun ….but also present participle is not ok.

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I GOT THE CORRECT ANSWER.
JUST HAVE A DOUBT IN OPTION B
IN OPTION B:DOES "WHICH TOOK PLACE AFTER 50 YEARS " MODIFY "THE PREDICTIONS" ?

Some 200 world-famous physicists recently attended a conference whose purpose not only was to consider the prospects for the next 50 years of research in physics but also assessing the accuracy of the predictions made at the last meeting of this type, which took place 50 years earlier.

(A) not only was to consider the prospects for the next 50 years of research in physics but also assessing the accuracy of the predictions made at the last meeting of this type,
(B) not only was considering the prospects for the next 50 years of research in physics but also assessing the accuracy of the predictions which were made at the last meeting of this type and
(C) was not only considering the prospects for the next 50 years of research in physics but also to assess the accuracy of the predictions made at the last meeting of this type and
(D) was not only to consider the prospects for the next 50 years of research in physics but also to assess the accuracy of the predictions made at the last meeting of this type,
(E) was to consider not only the prospects for the next 50 years of research in physics but also assessing the accuracy of the predictions made at the last meeting of this type,


is construction of idiom Not only X , but also Y is correct. please tell me weather we can separate idiom by inserting comma?

Thanks
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JAIN09 , I assume you intended to refer to the phrase "which took place 50 years earlier"?

(B) Some 200 world-famous physicists recently attended a conference whose purpose not only was considering the prospects for the next 50 years of research in physics but also assessing the accuracy of the predictions which were made at the last meeting of this type and which took place 50 years earlier.

Yes, "which" in option B incorrectly modifies "predictions."
The word and creates a list that describes predictions.
The list is composed of two which clauses that have equal weight and are parallel.

Hope that helps.

The rest of this post is about meaning. Read no further if you are satisfied with the answer in boldface type.
The parallel which-clause structure creates an incorrect meaning. The predictions
• were made at the last meeting of this type and
• took place 50 years earlier

Wrong. The meeting took place 50 years earlier, not the predictions.
How do we know? Not because (A) says so.
Myth: Option (A) determines the meaning of the sentence.
Fact: Option (A) does NOT determine the meaning of the sentence.

We know that the predictions did not take place 50 years earlier because predictions do not "take place."
"Take place" means: happen, occur, or come about.

Predictions do not just happen. Predictions are actively made.

Further, options A, D, and E, in which the meeting took place 50 years earlier, can give guidance.
Which fact makes makes more sense:
(1) the meeting took place 50 years earlier, or
(2) the predictions took place 50 years earlier?

This meeting considered what might happen in the next 50 years of physics.
It makes sense that a meeting in the present would consider predictions
made in a similar meeting that was held 50 years earlier.

Every 50 years the profession assesses its future.

I bring up the meaning analysis because this question uses an unusual structure.

We do not have to address the meaning of B.
B is grammatically incorrect.
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sonusaini1 - Yes, the idiom "not only X but also Y" can be separated by a comma, thus:
"Not only X, but also Y."
In fact, the idiom often IS separated by a comma.
HERE is an official question that inserts a comma.

Although THIS POST does not discuss the comma question, the post contains examples that include a comma insertion and a semicolon insertion.
Hope that helps.
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generis carcass daagh

can you tell "this" is been referred to which entity?

conference whose purpose == this ( whose purpose xxx) type ( conference)

OE:
Parallelism; Idiom; Logical predication
This sentence uses the idiomatic expression not only X but also Y to
present two purposes of the conference. This expression requires parallel
constructions. In this sentence, not only . . . but also . . . should follow
the verb was, making both purposes predicate nominatives.
A. The verb was should come before the idiom not only . . . but also . . .
; the two purposes are not expressed in parallel form; to consider is
an infinitive phrase, and assessing is a gerund.
B. As in (A), the verb is misplaced; the use of the conjunction and in
place of the relative pronoun which near the end of the sentence
nonsensically links the verb took place with the subject purpose.
C. The verbs considering and to assess are not parallel; as in (B), the
conjunction and nonsensically links the verb took place with the
subject purpose.
D. Correct. This sentence presents both purposes in parallel form.
E. The verbs to consider and assessing are not parallel.
The correct answer is D.

Hi ExpertsGlobal5 or any other expert,

Can you please tell me what "whose" is referring to?

Purpose being a plural verb, "whose" must refer to plural noun. I guess.

Thank you for taking out time and resolving my doubt.

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