Tamil is a Dravidian language, spoken by over 70 million people in India, Sri Lanka, Malaysia, Singapore, and other countries. It is the oldest language in the world with a continuous literary tradition, dating back over 2,000 years. Tamil is also one of the 22 official languages of India.
Indo-Aryan languages are a branch of the Indo-European language family, spoken by over 2 billion people in Asia and Europe. The most widely spoken Indo-Aryan languages are Hindi, Bengali, and Urdu.
Sino-Tibetan languages are a family of languages spoken by over 1.5 billion people in Asia. The most widely spoken Sino-Tibetan languages are Mandarin Chinese, Cantonese, and Tibetan.
Dravidian languages are a family of languages spoken by over 250 million people in India, Sri Lanka, Pakistan, and Bangladesh. The most widely spoken Dravidian languages are Tamil, Telugu, Kannada, and Malayalam.
Austroasiatic languages are a family of languages spoken by over 120 million people in Southeast Asia, East Asia, and the Indian subcontinent. The most widely spoken Austroasiatic languages are Vietnamese, Khmer, and Mon.
Therefore, the correct answer is (c).