The correct answer is: Sutlej.
The Sutlej is the longest river in Himachal Pradesh, India. It is a tributary of the Indus River, and is the easternmost of the five rivers that flow through the Punjab region. The Sutlej originates in the Himalayas, and flows through Himachal Pradesh, Punjab, Haryana, and Rajasthan before joining the Indus River in Pakistan. The Sutlej is a major source of irrigation and hydroelectric power in India.
The Chenab is the second longest river in Himachal Pradesh. It originates in the Himalayas, and flows through Himachal Pradesh, Jammu and Kashmir, and Punjab before joining the Indus River in Pakistan. The Chenab is a major source of irrigation and hydroelectric power in India.
The Ravi is the third longest river in Himachal Pradesh. It originates in the Himalayas, and flows through Himachal Pradesh, Punjab, and Pakistan before joining the Chenab River. The Ravi is a major source of irrigation and hydroelectric power in India.
The Beas is the fourth longest river in Himachal Pradesh. It originates in the Himalayas, and flows through Himachal Pradesh, Punjab, and Pakistan before joining the Sutlej River. The Beas is a major source of irrigation and hydroelectric power in India.