By pressing a tiny amount of nitrogen between two diamonds to a pressu

By pressing a tiny amount of nitrogen between two diamonds to a pressure of 25 million pounds per square inch, scientists not only were able to transform the gas into a solid, but they also created a semiconductor similar to silicon.

(A) not only were able to transform the gas into a solid, but they also created -- Not only X , but also Y -- parallelism issue -- they in part after that
(B) not only were able to transform the gas into a solid but also creating -- parallelism issue
(C) were able not only to transform the gas into a solid but to create - Correct
(D) were able not only to transform the gas into a solid but also creating -- parallelism issue
(E) were not only able to transform the gas into a solid, but they were also able to create -- parallelism issue -- they in the part after but
Answer C
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Parallelism is the most fundamental error in all of GMAT SC! don't look at ANY other type of error until you've considered basic parallelism!

*****
IN ACTUALITY, there is really only one base structure here, which is "not ... but ..."

that's actually the only TRUE set of parallel markers here. "only" and "also" are adverbs, and so ultimately function as modifiers -- i.e., they aren't necessary to the structure.
still, since "not only ... but also ..." is so common, you may want to memorize it separately -- but be aware that this is NOT the only correct form of this idiom.

the MOST reliable way to deconstruct this idiom is just to memorize "not ... but ...", and then ignore the adjectives "only" and "also" in deciding whether structures are grammatically parallel.
in deciding the MEANING of the structure, you can't dismiss "only" and "also" ... but that's a separate issue. see below.

--

EXAMPLES:
BE SURE YOU CAN UNDERSTAND WHY EACH OF THESE IS CORRECT OR INCORRECT

the writer was not only mortified by her mistake but determined to correct it in print.
--> CORRECT

the writer not only was mortified by her mistake but was determined to correct it in print.
--> CORRECT

the writer was not only mortified by her mistake but was determined to correct it in print.
--> INCORRECT

the small child was relieved to hear that the rustling under the bed was caused not by a ghost but by his pet cat.
--> CORRECT

the small child was relieved to hear that the rustling under the bed was caused not by a ghost but his pet cat.
--> INCORRECT

--

SO WHAT'S THE DIFFERENCE, THEN, WITH
"not only ... but also ..."
"not only ... but ..."
"not ... but ..."
?

the difference here is strictly one of MEANING.

the first two are pretty similar; the last one is TOTALLY different.

(1) "not only ... but also ..." is used to refer to two descriptions that REINFORCE each other (i.e., both have the same connotation -- two good things, two bad things, two helpful things, etc.), but are fundamentally independent.
ex:
this drug is not only an alertness aid, but also an antidepressant.
--> "alertness aid" and "antidepressant" are TWO GOOD THINGS that have basically NOTHING TO DO WITH EACH OTHER.
therefore, "not only ... but also".

(2) "not only ... but ..." is also used to refer to two descriptions that REINFORCE each other, but it's generally used when the second description EXPANDS or GOES BEYOND the first.
ex:
ryan not only competed in all the events, but won first prize in three of them.
--> note that "won first prize in three of [the events]" is an EXTENSION of "compet[ing] in all the events". these are not independent.

the above difference between (1) and (2) is subtle, and is therefore not terribly important. however, you MUST be able to tell those from the next one:

(3) "not ... but ..." is used when the FIRST thing is EXPECTED, ASSUMED, or PREVIOUSLY THOUGHT, but is REFUTED / CONTRADICTED / DISPROVED by the SECOND thing.
ex:
the snacks known as "french fries" were invented not in france, but in belgium.
--> the initial assumption, which is refuted, is that french fries are from france.


********
grammatical elements that FOLLOW parallel signals (not including modifiers/adjectives/adverbs, which can be neglected in considering grammar unless they ARE the whole parallel structures) must be parallel.
example:
The author not only published her paper, but SHE also won a prize.

following the signal not is "published her paper" -- notice that you don't have to consider "only" in this analysis, since it's an adverb and is therefore grammatically disposable
following the signal but is "SHE (also) won..."
these aren't parallel.
a subject is clearly not a grammatically disposable element (modifier), so there's no way in which these constructions can be considered parallel.


*****
"The drug not only kills the bacteria but also kills white cells"
(note: no comma necessary) --> this doesn't make sense. the construction "not only ... but also" should only be used when the two things actually reinforce each other (i.e., have SIMILAR effects/contexts).
the key observation here is that killing the bacteria is GOOD, but that killing white blood cells is BAD. Those are opposites -- one good, one bad -- so the context here is inappropriate.
for instance,
The drugs not only kills the bacteria but also alleviates joint pain--> this one makes sense, since both effects described are positive.

This example would be better written with just "but":
"The drug kills the bacteria but also kills white cells"
that makes sense.



******
"The Acme Battery Corporation does not only make batteries; it also makes battery accessories, such as chargers."
in this case, the meaning is largely the same as that of "not only ... but also..."


*******
basically, as long as 2 parallel structures have the same basicform / grammatical role -- irrespective of add-ons like modifiers -- they're legitimately parallel structures.

e.g.

i have a truck and a bicycle.
--> parallel

i have a big, red, rusty old truck, which has been driven over 250,000 miles, and a bicycle.
--> still parallel.


********
basically, here's the difference:

• "not X but Y": 
this construction implies that X is what's "normal" or "expected", and that Y is what's actually true.
e.g.,
I was surprised to learn that Ella was not Clint's biological daughter but in fact his adopted daughter, since her facial features so closely resemble his.
(here, since the girl looks so much like her dad, we EXPECT to find out that she's his biological daughter.)

• "X but Y": 
this just implies a contrast, but NOT any expectation.
(in THIS PARTICULAR sentence—as already explained in this thread—the "X" part includes the word "not".)
e.g.,
I am not a mechanic, but can perform basic maintenance on non-hybrid cars.

__

this sentence DOES describe a contrast—these things aren't products of natural selection, BUT they ARE products of essentially random selection processes.

on the other hand, it DOES NOT describe any sort of situation with an "expected" or "predictable" result.

thus it should not use the first construction; it should use the second one.
to make this sentence into "X, but Y", we need to include the are on the right-hand side.


******
If you have a two-part parallel construction - such as "not only ... but also" - your detection of parallelism (or lack thereof) should be COMPLETELY mechanical. just look at the words that follow the first part, and look at the words that follow the second part (and DON'T ignore any words). if they don't have the same grammatical structure, then the parallelism is faulty. end of story. 

choice (a): 
not only were able to transform the gas into a solid, but they also created 
the blue parts aren't parallel, because there's a subject in the second part but not in the first. and you are not, not, NOTallowed to ignore "they" in the second part. 
and because "scientists" comes before "not only", you must ignore it.

Posted from my mobile device
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What makes option E grammatically incorrect?

What makes option E grammatically incorrect?

There is a way to check in not only X but also Y or not only X but Y construction whether selected choice is correct.

<Modifier>....., scientists not only were able to transform the gas into a solid, but they also created a semiconductor similar to
silicon.

So, scientists were able to do two things which should stand independently by themselves.

A. not only were able to transform the gas into a solid, but they also created
B. not only were able to transform the gas into a solid but also creating
C. were able not only to transform the gas into a solid but to create
D. were able not only to transform the gas into a solid but also creating
E. were not only able to transform the gas into a solid, but they were also able to create

Choice C:
Scientists were able not only to transform the gas into a solid.
Scientists were able but to create a semiconductor similar to silicon.

Both are independent sentences that can stand by their own.This method has helped me quickly eliminate choices in this type of construction.Like in this sentence, choices B & D can be eliminated easily. Hope it helps you too!

this is hard. this question tells us not to focus on forms of words but to focus on meaning . if we focus on meaning, we can accept choice C and escape from other choices.

in choice c, we need "also". but choice C equates "to transform" and " to create" even it lack "also". so, the meaning is clear though "also" is lacking. C is acceptable.
choice A equate "were able to transform" to "create". this is wrong.
choiceB equates "were able to transform" to "creating". this is not logic
choice d equates "to transform" to "creating". this is not logic.

choice e is hard.
first "they " is between "but" and "also" whereas "scientist " is outside "not only". this is terrible.
even if choice e logically equates "able to transform" and "able to create" because these phrases stand after "only" and "also", it is inferior because "able" is repeated.

so, choice C , though not parallelism in form, offer parallelism in meaning and ,so, is good.
we can argue that choice e also offer parallelism in meaning. but choice E present "able" 2 times. this is inferior to choice C.

the purpose of parallelism is to offer a logic, which is a parallelism in meaning. if we think this way, we will accept choice C easily even though choice C lacks "also". the lack of "also" dose not affect the parallelism in meaning.

I get that, but could you please tell me how did you eliminate E? Apart from the "not only" part.

Important lesson
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a, b , d and e all have parallelism problem .only c has proper parallelism.

This question is based on Parallelism.

The sentence contains the correlative conjunctions ‘not only-but also’. To maintain parallelism, the appropriate pair of conjunctions must be used and each of the pair of conjunctions must be followed by a word of the same part of speech.

In Option A, the conjunction ‘not only’ is followed by the verb ‘were’ but the conjunction ‘but also’ is split up with the pronoun ‘they’ in between the conjunction. The infinitive form “to transform” is used after the first of the pair but is not repeated after the second of the pair of conjunctions. So, Option A can be eliminated.

In Option B, the conjunction ‘not only’ is followed by the verb ‘were’; the conjunction ‘but also’ is however followed by the participle ‘creating’. So, Option B can be eliminated.

In Option D, ‘not only’ is followed by the infinitive form ‘to transform’ but the second of the pair is followed by the participle form ‘creating’. So, Option D can be eliminated.

Option E is wordy. The verb ‘were’ is repeated unnecessarily. So, Option E can be eliminated.

This option maintains parallelism even though the second conjunction is 'but'; this can be an appropriate pair of conjunctions too. Both the conjunctions ‘not only’ and ‘but’ are followed by infinitive forms. Therefore, C is the most appropriate option.

Jayanthi Kumar.
_________________

Ron's Explanation

actually, here's a more accurate take on what's going on here.

IN ACTUALITY, there is really only one base structure here, which is "not ... but ..."

that's actually the only TRUE set of parallel markers here. "only" and "also" are adverbs, and so ultimately function as modifiers -- i.e., they aren't necessary to the structure.
still, since "not only ... but also ..." is so common, you may want to memorize it separately -- but be aware that this is NOT the only correct form of this idiom.

the MOST reliable way to deconstruct this idiom is just to memorize "not ... but ...", and then ignore the adjectives "only" and "also" in deciding whether structures are grammatically parallel.
in deciding the MEANING of the structure, you can't dismiss "only" and "also" ... but that's a separate issue. see below.

--

EXAMPLES:
BE SURE YOU CAN UNDERSTAND WHY EACH OF THESE IS CORRECT OR INCORRECT

the writer was not only mortified by her mistake but determined to correct it in print.
--> CORRECT

the writer not only was mortified by her mistake but was determined to correct it in print.
--> CORRECT

the writer was not only mortified by her mistake but was determined to correct it in print.
--> INCORRECT

the small child was relieved to hear that the rustling under the bed was caused not by a ghost but by his pet cat.
--> CORRECT

the small child was relieved to hear that the rustling under the bed was caused not by a ghost but his pet cat.
--> INCORRECT

--

SO WHAT'S THE DIFFERENCE, THEN, WITH
"not only ... but also ..."
"not only ... but ..."
"not ... but ..."
?

the difference here is strictly one of MEANING.

the first two are pretty similar; the last one is TOTALLY different.

(1) "not only ... but also ..." is used to refer to two descriptions that REINFORCE each other (i.e., both have the same connotation -- two good things, two bad things, two helpful things, etc.), but are fundamentally independent.
ex:
this drug is not only an alertness aid, but also an antidepressant.
--> "alertness aid" and "antidepressant" are TWO GOOD THINGS that have basically NOTHING TO DO WITH EACH OTHER.
therefore, "not only ... but also".

(2) "not only ... but ..." is also used to refer to two descriptions that REINFORCE each other, but it's generally used when the second description EXPANDS or GOES BEYOND the first.
ex:
ryan not only competed in all the events, but won first prize in three of them.
--> note that "won first prize in three of [the events]" is an EXTENSION of "compet[ing] in all the events". these are not independent.

the above difference between (1) and (2) is subtle, and is therefore not terribly important. however, you MUST be able to tell those from the next one:

(3) "not ... but ..." is used when the FIRST thing is EXPECTED, ASSUMED, or PREVIOUSLY THOUGHT, but is REFUTED / CONTRADICTED / DISPROVED by the SECOND thing.
ex:
the snacks known as "french fries" were invented not in france, but in belgium.
--> the initial assumption, which is refuted, is that french fries are from france.

By pressing a tiny amount of nitrogen between two diamonds to a pressure of 25 million pounds per square inch, scientists not only were able to transform the gas into a solid, but they also created a semiconductor similar to silicon.

(A) not only were able to transform the gas into a solid, but they also created -> Incorrect.
(B) not only were able to transform the gas into a solid but also creating -> Incorrect.
(C) were able not only to transform the gas into a solid but to create -> Correct.
(D) were able not only to transform the gas into a solid but also creating -> Incorrect.
(E) were not only able to transform the gas into a solid, but they were also able to create -> Incorrect.

So, I think C.

Hi,

In choice A]

(A) not only were able to transform the gas into a solid, but they also created

''were able' is a verb form parallel to '' created'' Is my understanding correct?

Is there a problem in using 'they' in b/w 'but ..also'

Yeah Himanshu, one would typically expect a "parallel structure" with "not...but".

Since "not" is followed by a "verb" ("were", along with the modifier "only"), we should have another "verb" immediately after "but".
_________________

Hello himanshu0123,

We hope this finds you well.

To answer your query, the inclusion of "they" forms an independent clause on one side of the parallelism marker, thus breaking parallelism with the verb phrase "were able to transform".

We hope this helps.
All the best!
Experts' Global Team
_________________

ExpertsGlobal5
That was very splendid explanation!

By pressing a tiny amount of nitrogen between two diamonds to a pressure of 25 million pounds per square inch, scientists not only were able to transform the gas into a solid, but they also created a semiconductor similar to silicon.

Option Elimination -
But before that, let's understand the usage of "not only X but also Y" and "not only X but Y" - both usages are correct.
"not only X but also Y" - The structure is used to present two parallel elements that are both important and contribute to the overall meaning of the sentence. The elements are typically balanced in structure and meaning. E.g., She is not only intelligent but also diligent.
"not only X but Y" - This structure is used when the second element is a consequence or result of the first element. E.g., He not only studied hard but passed the exam with flying colors. Here, "not only" introduces the action of studying hard, "but" introduces the result or consequence of that action, which is passing the exam with flying colors.

(A) not only were able to transform the gas into a solid, but they also created - The structure of X and Y is not parallel. There is no need to repeat "they." Were applies to both and has to be outside "not only"
(B) not only were able to transform the gas into a solid but also creating - The structure of X and Y is not parallel
(C) were able not only to transform the gas into a solid but to create - perfect.
(D) were able not only to transform the gas into a solid but also creating - The structure of X (infinitive) and Y (ING verbal) is not parallel
(E) were not only able to transform the gas into a solid, but they were also able to create - We already have a common "were" why to repeat "were" after but. Moreover, no reason to repeat "they" again.