What is the most correct geological basis for calling Narmada valley a rift valley?

Correct answer: It flows westward between crustal faults

The direct answer is A: the Narmada flows westward through a valley controlled by crustal faults, so it is called a rift valley river. A rift valley forms when movements and fractures in the Earth’s crust create a depressed zone between faults. The Narmada follows such a structurally controlled valley between the Vindhya and Satpura regions and finally reaches the Arabian Sea. Therefore option A gives the correct geological basis. Option B is wrong because Narmada is not a northern tributary of the Ganga; it is a major west-flowing peninsular river. Option C is wrong because it is not located in the Ganga-Brahmaputra delta. Option D is wrong because Narmada is not a distributary of the Luni; Luni is a separate river of Rajasthan. The important reasoning chain is: crustal faults create a depressed linear valley; the river follows that valley; hence Narmada is associated with a rift valley. Memory cue: Narmada and Tapi are famous west-flowing rivers; Narmada is especially linked with a rift valley.