The Nellai dialect, known for its distinct pronunciation, is spoken in the region of:

Tirunelveli
Kanchipuram
Vellore
Salem

The correct answer is: a) Tirunelveli.

The Nellai dialect is a dialect of Tamil spoken in the Tirunelveli district of Tamil Nadu, India. It is known for its distinct pronunciation, which is characterized by a strong emphasis on the consonants and a tendency to drop the vowels. The Nellai dialect is also known for its unique vocabulary, which includes many words that are not found in other dialects of Tamil.

The other options are incorrect because they are not regions where the Nellai dialect is spoken. Kanchipuram is a city in the Kanchipuram district of Tamil Nadu. Vellore is a city in the Vellore district of Tamil Nadu. Salem is a city in the Salem district of Tamil Nadu.