Fertile riverine alluvial soil is best suited for producing _________.

The correct option/answer is Rice.

Alluvial soil is formed by the deposition of silt and sediment brought down by rivers. It is highly fertile due to its rich mineral content and fine texture, which gives it excellent water-retaining properties. Rice is a crop that requires a high amount of water and clayey or alluvial soil that can retain moisture for a long duration during its growth cycle. Therefore, fertile riverine alluvial soil is best suited for producing rice.

Let us look at why other options are less suited:
- Tea requires well-drained loamy soil, often on hill slopes, to prevent waterlogging.
- Cotton grows best in black soil (also known as regur soil), which has high clay content and excellent moisture retentivity but is different from riverine alluvial soil.
- Corn (maize) grows well in a variety of soils but prefers deep, rich soils with good drainage, rather than water-retaining clayey alluvial plains typical of rice cultivation.