Correct option is A
The correct answer is (a) Bhagirathi and Alaknanda at Dev Prayag.
The Ganga River is formed by the confluence of the Bhagirathi and Alaknanda rivers at Dev Prayag, a town in the Tehri Garhwal district of Uttarakhand. At this confluence, the Bhagirathi, which originates from the Gangotri Glacier, merges with the Alaknanda, which has its source near the Satopanth Glacier. This union marks the beginning of the Ganga River's journey through the plains of northern India.
Additional Information:
Bhagirathi and Alaknanda at Karna Prayag: Karna Prayag is another confluence in Uttarakhand where the Alaknanda meets the Pindar River, not the Bhagirathi.
Bhagirathi and Alaknanda at Gangotri: Gangotri is the origin of the Bhagirathi River, but it is not the confluence point with the Alaknanda.
Bhagirathi and Alaknanda at Rudra Prayag: Rudra Prayag is the confluence of the Alaknanda and Mandakini rivers, not the Bhagirathi.