Which one of the following rivers flows through a rift valley?
A.Narmada
B.Mahanadi
C.Godavari
D.Krishna

Hint: A rift valley is a linear-shaped lowland formed between surrounding highlands and mountains because the Earth’s tectonic plates have moved apart in this region. It is formed on a divergent plate boundary and subsequently deepened by agents of erosion. The East African Rift and the Baikal Rift Zone are two active continental rifts. Several lakes and water bodies lie in rift valleys today which include the Dead Sea, Lake Baikal, Lake Tanganyika, Lake Superior, Lake Vostok, etc.

Complete Answer:
Option A: is correct. Narmada along with Tapi and Mahi are the only three rivers in the Indian Peninsula that flow from east to west. It is also one of the only rivers to flow through the rift valley between the Vindhya and Satpura ranges that was caused due to recession of the sea because of tectonic disturbances and empties into the Arabian sea. Tapti and Mahi are the other two rivers that flow through a rift valley but in between other ranges.
Options B, C and D: are incorrect. All three of these, Mahanadi, Godavari and Krishna are rivers flowing from west to east in the Indian peninsula. They flow in this direction due to the natural slope of the Western Ghats and the Deccan Plateau and empty into the Bay of Bengal.

Note: Rift valleys differ from the river and glacial valleys because unlike these, rift valleys are not formed through erosion but through the movement of tectonic plates. Tectonic plates are constantly shifting against each other in fault zones, falling beneath one another in a process called subduction, crashing against one another at convergent plate boundaries, and tearing apart from each other at divergent plate boundaries.