Correct Option
The correct option is (a).
Explanation
The work of a river involves three main stages: the upper course (erosion dominant), the middle course (transportation dominant), and the lower course (deposition dominant). The velocity and landforms created by the river vary significantly across these stages due to changes in gradient and sediment load.
Statement-wise Analysis
- Statement 1 is Correct: In the upper course, the river flows over steep terrain. When the river water tumbles at a steep angle over very hard rocks or down a steep valley side, it forms a waterfall. This is a primary erosional feature of the youthful stage of a river.
- Statement 2 is Incorrect: As the river approaches the sea (lower course), the slope of the land becomes very gentle. Consequently, the speed of the flowing water decreases significantly, rather than becoming very fast. The reduced velocity leads to the deposition of the sediment load carried by the river.
- Statement 3 is Incorrect: Due to the slow speed and heavy load of sediments, the main river breaks up into numerous smaller channels known as distributaries. Each distributary flows into the sea and forms its own mouth. The collection of sediments from all these mouths contributes to the formation of a delta.
Key Takeaway: River velocity decreases as it approaches the sea due to a gentle gradient, leading to deposition. Distributaries are characteristic of the lower course, and each forms a distinct mouth where it enters the ocean.