Alluvial soil is the correct answer because it is highly fertile and well-drained, making it suitable for rice cultivation. It is formed by the deposition of sediments carried by rivers, which results in a rich composition of minerals and organic matter. This type of soil retains moisture, has good water-holding capacity, and allows for easy root penetration, all of which are essential for the healthy growth of rice plants. Additionally, alluvial soil is found in river basins and floodplains, which provide the necessary water supply for rice cultivation.