15. 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（D）

(E) originating from diverse ethnic and cultural heritages and perpetuating

我的困惑是the decline应该是和language variations并列吧？为什么language variations前面没有and？

盼明眼人赐教！