The correct answer is: d) All of the above.
Alluvial soils are a type of soil that is formed from the deposition of sediments by water. They are typically found in river valleys and floodplains. Alluvial soils are very fertile and are often used for agriculture.
The texture of alluvial soils can vary depending on the source of the sediments and the way in which they are deposited. Sandy alluvial soils are composed of mostly sand particles, while clayey alluvial soils are composed of mostly clay particles. Silty alluvial soils are composed of a mixture of sand, silt, and clay particles. Loamy alluvial soils are composed of a mixture of sand, silt, clay, and organic matter.
In Bihar, alluvial soils can range from sandy to clayey, rocky to gravelly, silty to loamy, and all of the above. The texture of the soil depends on the source of the sediments and the way in which they are deposited.