The correct answer is: c) Teesta.
The Teesta River is a major river in the eastern Himalayas. It flows through the Indian states of Sikkim, West Bengal, and Assam, and the Bangladesh districts of Rangpur, Dinajpur, and Jalpaiguri. The Teesta is a major source of hydropower in Sikkim and West Bengal.
The Brahmaputra River is the largest river in India and the third largest river in Asia. It flows through the Indian states of Arunachal Pradesh, Assam, and Meghalaya, and the Bangladesh districts of Mymensingh, Jamalpur, and Tangail. The Brahmaputra is not a major source of hydropower in Sikkim.
The Ganges River is the longest river in India and the second longest river in Asia. It flows through the Indian states of Uttarakhand, Uttar Pradesh, Bihar, Jharkhand, and West Bengal, and the Bangladesh districts of Rajshahi, Pabna, and Faridpur. The Ganges is not a major source of hydropower in Sikkim.
The Indus River is the longest river in Pakistan and the fifth longest river in Asia. It flows through the Indian states of Jammu and Kashmir, Himachal Pradesh, and Ladakh, and the Pakistani provinces of Punjab, Khyber Pakhtunkhwa, and Sindh. The Indus is not a major source of hydropower in Sikkim.