Sentence Correction

The increased popularity and availability of televisions has led to the decline of regional dialects, language variations which originate from diverse ethnic and cultural heritages and perpetuated by geographic isolation.
A. which originate from diverse ethnic and cultural heritages and perpetuated
B. that originated from diverse ethnic and cultural heritages and perpetuated
C. originated from diverse ethnic and cultural heritages and perpetuated
D. originating from diverse ethnic and cultural heritages and perpetuated
E. originating from diverse ethnic and cultural heritages and perpetuating

A- need ,which -- wrong
B- that and (that is missing) - wrong
C- originated (verb)- wrong ( complete sentence, complete sentence - worng)
D- ok
E- Language variation itself is perpetuating not by someone else - wrong
[spoiler]OA:D[/spoiler]

My question is about non- underlined about
The increased popularity and availability of televisions has led to the decline of regional dialects.
verb - has
subject - ??? not tevelisions as it after preposition
The increased popularity and availability , seems like 2 things
The increased popularity of TVS and increased availability of TV ....(then the subject is plural)
Can someone help me understand what is the subject and how is it different from above sentence

amnesty17 wrote: My question is about non- underlined about
The increased popularity and availability of televisions has led to the decline of regional dialects.
verb - has
subject - ??? not tevelisions as it after preposition
The increased popularity and availability , seems like 2 things
The increased popularity of TVS and increased availability of TV ....(then the subject is plural)
Can someone help me understand what is the subject and how is it different from above sentence

In RARE instances, a compound subject -- X and Y -- may be considered ONE UNIT and thus will take a singular verb.
To illustrate:
Peanut butter and jelly is my favorite type of sandwich.
Here, peanut butter and jelly represents ONE type of sandwich.
Hence, the verb is singular.

For an example in the OG13, check my post here:
https://www.beatthegmat.com/sc-ques-t113015.html

Please note the following:
In both the SC here and the one in the OG13, the combination of compound subject + singular verb appears only in the NON-UNDERLINED portion -- an indication that neither SC is testing this concept.
It is VERY unlikely that this concept will be tested in the UNDERLINED portion of an official SC.