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

Why D and not B/C?

The increased popularity and availability of televisions has led

Why isnt it "have"?

Can someone please tell in D....."perpetuated" is parallel to what ?

The increased popularity and availability of televisions has led

Why isnt it "have"?

IMO D..

Well the main sentence is:

The increased popularity and availability of televisions has led to the decline of regional dialects.

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What are regional dialects:

Regional dialects are language variations [we need a present participle here as its not a thing of the past.. its still present, so we use originating] originating from diverse ethnic and cultural heritages and perpetuated [past participle in parallel with the present participle used... ] by geographic isolation.