Sentence Correction

According to scholars, the earliest writing was probably not a direct rendering of speech, but was more than likely to begin as a separate and distinct symbolic system of communication, and only later merged with spoken language
a. Was more likely to begin as
b. More than likely began as
c. More than likely beginning from
d. It was more than likely begun from
e. It was more likely that it began

OA B
I have a number of doubts here. If comma+fanboys separate 2 independent clauses then shouldn't the clause after 'but' be independent
Again the explanation says that if we make this clause independent, as in option D, then the comma after communication must be omitted. Again, since there are no dependent markers before the beginning of 3rd clause i.e. 'only later merged with spoken language' so even the 3rd clause is independent. In this case, isn't it correct that the 2 clauses be separated by comma+and

I posted an explanation here:

https://www.beatthegmat.com/according-to ... 55-15.html

The primary issue here is parallelism. There are three actions attributed to the earliest writing:
it WAS probably not...but more than likely BEGAN...and only later MERGED...

Only B offers the needed parallelism.

Punctuation issues are rarely tested on the GMAT. There are only two types of punctuation errors that I would cite to eliminate answers:
COMMA SPLICE -- If a comma can be replaced by a period, eliminate the answer choice.
SEMI-COLON -- If a semi-colon cannot be replaced by a period, eliminate the answer choice.