Which major river of India forms a significant part of the southern border of Meghalaya?

The correct answer is: b) Barak River.

The Barak River is a major river in northeastern India. It is the largest tributary of the Brahmaputra River. The Barak River originates in the Manipur Hills and flows through the states of Manipur, Mizoram, and Assam. It forms a significant part of the southern border of Meghalaya. The Barak River is a major source of irrigation and drinking water for the people of the region. It is also a popular destination for fishing and boating.

The other options are incorrect because:

• The Brahmaputra River is the largest river in India. It flows through the states of Arunachal Pradesh, Assam, and Meghalaya. It does not form a significant part of the southern border of Meghalaya.
• The Ganga River is the second largest river in India. It flows through the states of Uttarakhand, Uttar Pradesh, Bihar, Jharkhand, and West Bengal. It does not form a significant part of the southern border of Meghalaya.
• The Teesta River is a major river in northeastern India. It is a tributary of the Brahmaputra River. The Teesta River flows through the states of Sikkim, West Bengal, and Assam. It does not form a significant part of the southern border of Meghalaya.