The major river systems in Himachal Pradesh drain into the Indus Basin. The Indus River is the largest river in Pakistan and the second-largest river in India, after the Ganges. It is the principal river of the Indus River basin, which is one of the most important river systems in Asia. The Indus River basin covers an area of about 1,165,000 square kilometers (450,000 square miles), and is home to over 300 million people. The Indus River originates in the Tibetan Plateau, and flows through India and Pakistan before emptying into the Arabian Sea. The Indus River is a major source of water for irrigation, drinking water, and hydroelectric power for both India and Pakistan. The Indus River is also an important transportation route, and is used for both commercial and passenger traffic.
The other options are incorrect because they do not drain into the Indus Basin. The Ganga River is the longest river in India, and is the principal river of the Ganges River basin. The Ganges River basin covers an area of about 1,000,000 square kilometers (386,000 square miles), and is home to over 400 million people. The Ganges River originates in the Himalayas, and flows through India before emptying into the Bay of Bengal. The Ganges River is a major source of water for irrigation, drinking water, and hydroelectric power for India. The Ganges River is also an important religious site for Hindus, and is considered to be sacred by many Hindus.
The Brahmaputra River is the longest river in India and Bangladesh, and is the principal river of the Brahmaputra River basin. The Brahmaputra River basin covers an area of about 930,000 square kilometers (360,000 square miles), and is home to over 400 million people. The Brahmaputra River originates in the Himalayas, and flows through India, Bhutan, and Bangladesh before emptying into the Bay of Bengal. The Brahmaputra River is a major source of water for irrigation, drinking water, and hydroelectric power for India and Bangladesh. The Brahmaputra River is also an important transportation route, and is used for both commercial and passenger traffic.
Both the Ganga River and the Brahmaputra River are major rivers in India, but they do not drain into Himachal Pradesh. The Indus River is the only major river that drains into Himachal Pradesh.