Sentence Correction (SC) | Re: According to mathematical scholars, the ancient conception of the numb

Can anyone give reasoning for each answer choice. Appreciate it.

Alsoarun6765 can you please clarify the following please:

1. In your explanations above in regards to parallelism, what are the two elements that are parallel? Are they both prepositional phrases or do they both have a verb?
2. Can the idiom "Not X but Y" have a comma in the middle such as John is not a student, but a professor. -> is this correct?