Correct Option (a): 1 only
The Narmada River's unique westward flow, unlike most other large peninsular rivers, is primarily due to its course through a linear rift valley. This rift valley is a geological depression formed by tectonic activity, bounded by fault lines. It is situated between the Vindhya Range to the north and the Satpura Range to the south. This structural control of the rift valley dictates the river's gradient and direction, causing it to flow westwards into the Arabian Sea.
- Statement 1 is correct: The Narmada occupies a linear rift valley, which is the fundamental geological reason for its westward flow. Rift valleys are depressions formed by the subsidence of land between two parallel faults, creating a distinct drainage path.
- Statement 2 is descriptive but not the primary explanation for the westward flow. While the Narmada does flow between the Vindhyas and Satpuras, it is the existence of the rift valley *within* this geographical corridor that determines its westward direction, rather than merely its location between the ranges.
- Statement 3 is incorrect: The general slope of the Indian Peninsular Plateau is towards the east, which is why most major rivers like the Godavari, Krishna, and Kaveri drain into the Bay of Bengal. The assertion that the land slopes to the west from Central India is factually incorrect as a general principle.
Incorrect Options
Options (b) and (c) are incorrect because they include statement 3, which misrepresents the general slope of the Peninsular Plateau. Option (d) is incorrect because statement 1 accurately identifies the primary reason for the Narmada's westward flow.