I stumbled upon a great explanation by "Ron". Sharing it for benefit of others
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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.
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.-->
CORRECTthe writer not only was mortified by her mistake but was determined to correct it in print.-->
CORRECTthe writer was not only mortified by her mistake but was determined to correct it in print.-->
INCORRECTthe small child was relieved to hear that the rustling under the bed was caused not by a ghost but by his pet cat.-->
CORRECTthe small child was relieved to hear that the rustling under the bed was caused not by a ghost but his pet cat.-->
INCORRECTSO 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".
Wrong: The drug
not only kills the bacteria
but also kills white cells. (Doesn’t make sense as explained, one good, one bad -- so the context here is inappropriate)
[Correct Version can be written with just “but”: The drug kills the bacteria but also kills white cells.]
Correct: The drugs not only kills the bacteria but also alleviates joint pain. (Both effects described are positive)
(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 "compete[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.
-->
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.)
[Other scenarios:
"not only....also..." This could work,
if there were some other
transition signal (e.g. a semicolon) to replace the missing "but".For instance:
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..."
"not only ... also" doesn't make grammatical sense; the inclusion of the conjunction "but" is of the utmost importance. If you don't have this conjunction, then the sentence thus created becomes a run-on
"not....but also..." Doesn't seem logical under any circumstances
"X but Y": this just implies
a contrast, but NOT any expectation.e.g.,
I am not a mechanic, but can perform basic maintenance on non-hybrid cars.]
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Hope it can explain why C is correct