The correct answer is: a) Retroflex consonants
Retroflex consonants are consonants that are articulated with the tongue tip curled back towards the hard palate. They are found in many languages of the Indian subcontinent, including Telugu.
Vowel harmony is a phonological phenomenon in which vowels in a word must agree in certain features, such as frontness or backness. It is found in many languages of the world, including Finnish and Turkish.
Nasalization is a phonological phenomenon in which vowels are pronounced with the nasal cavity open, resulting in a nasalized sound. It is found in many languages of the world, including French and Portuguese.
Borrowings from Tamil are words that have been borrowed from the Tamil language into the Telugu language. They are found in many dialects of Telugu, including the Rayalaseema dialect.
The Rayalaseema dialect of Telugu is spoken in the Rayalaseema region of Andhra Pradesh, India. It is characterized by its retroflex consonants, which are not found in other dialects of Telugu.