The correct option is (c).
Explanation
Rivers are primary agents of exogenic change, involved in erosion, transportation, and deposition. The material transported by a river, known as its load, is deposited when the velocity of the water decreases. This deposition leads to the formation of aggradational plains, such as alluvial fans, floodplains, and deltas.Statement 1 is Correct: The load deposited by rivers includes coarse materials such as stones, pebbles, and gravel. These heavier materials are typically deposited in the upper reaches of the plains (piedmont zone) where the river exits the mountains and its carrying capacity drops sharply. For example, the Bhabar belt in the Indo-Gangetic plains consists largely of cobbles and stones.
Statement 2 is Incorrect: Sand is a major constituent of river deposition. As the river moves downstream and its velocity moderates, medium-sized particles like sand are deposited to form features such as natural levees, point bars, and riverbeds. Asserting that sand is "never" part of the load is factually wrong.
Statement 3 is Correct: Silt and clay represent the fine-grained suspended load of a river. These particles settle slowly and are usually deposited over broad floodplains during inundation or in the deltaic regions where the river meets standing water. This fine sediment contributes significantly to the fertility of alluvial plains.
Key Takeaway: Alluvial plains are formed by the deposition of sediments (alluvium) of varying sizes, including stones, sand, silt, and clay, distributed according to the river's energy and distance from the source.