At which place do the Bhagirathi and the Alaknanda meet to form the Ganga?

The correct answer is C, Devprayag. At Devprayag in Uttarakhand the Bhagirathi, which comes down from the Gangotri glacier, meets the Alaknanda, and the united stream is called the Ganga from that point. Option A is wrong because Rudraprayag is the confluence of the Alaknanda with the Mandakini. Option B is wrong because Karnaprayag is where the Pindar joins the Alaknanda. Option D is wrong because Haridwar is the town where the Ganga leaves the mountains and enters the plains, an important fact in its own right but not a confluence of the two head streams. The five prayags of the Alaknanda, namely Vishnuprayag, Nandprayag, Karnaprayag, Rudraprayag and Devprayag, are worth learning in order, since papers ask which river joins at each of them. A second point examiners like is that the Bhagirathi is treated as the source stream of the Ganga even though the Alaknanda carries more water, and that the Gangotri glacier snout at Gaumukh is where the Bhagirathi itself begins.