The original manuscript of William Wordsworth’s long autobio

Hi nityamskhurana,

Check out the article here : markers-in-parallelism-139076.html
This should answer your question. But if used alone is a single word marker for parallelism

Sentence Meaning: The Original manuscript poet shows us that his ideas were not perfect and but were revised often over the course of many years

The original manuscript of William Wordsworth’s long autobiographical poem shows-------> This is an independent clause
that the poet normally perfected his ideas not immediately (Sub: The poet, Verb: Perfected )
but often revised his work over the course of many years.

Here looking in the context of the sentence the usage "the poet normally perfected his ideas not immediately" of not immediately is not correct and acts as a modifier

Thus option A and B can be ruled out

Now let's look at option C, D and E

E messes up the parllelism for Not X But Y where X and Y should be parallel

Usage of Past perfect Had revised is incorrect as the sentence says the work was revised over a course of many years and thus the revision may have occured at a later stage.

In Option C, The use of but is to bring contrast in the sentence and maintains the parallelism with that clause in the original sentence.

"The original manuscript of William Wordsworth’s long autobiographical poem shows
that the poet normally did not perfect his ideas immediately but
that he often revised his work over the course of many years.