The correct answer is: c) Indo-Tibetan speaking people.
The Vedic Age was a period in Indian history that lasted from about 1500 to 500 BCE. It was during this time that the Vedas, the sacred texts of Hinduism, were composed. The Vedas mention a number of tribes that lived in the region that encompasses modern-day Sikkim, including the Kiratas, the Bhotiyas, and the Lepchas. These tribes were all Indo-Tibetan speaking peoples.
The Dravidian tribes are a group of peoples who live in southern India and Sri Lanka. They are believed to have migrated to India from Africa around 5000 BCE. The Aryan settlers were a group of people who migrated to India from Central Asia around 1500 BCE. They spoke an Indo-Aryan language and were the ancestors of the modern-day Hindus. The Austroasiatic groups are a group of peoples who live in Southeast Asia. They speak an Austroasiatic language and are the ancestors of the modern-day Khmers, Vietnamese, and Malays.
The Indo-Tibetan speaking peoples are a group of peoples who live in the Himalayas and the Tibetan Plateau. They speak an Indo-Tibetan language and are the ancestors of the modern-day Tibetans, Nepalis, and Bhutanese.