The tea plantations of Assam thrive on:

The correct answer is: b) Fertile alluvial soil.

Alluvial soil is a type of soil that is formed by the deposition of sediments from rivers and streams. It is typically rich in nutrients and organic matter, making it ideal for growing crops. Tea plantations in Assam thrive on fertile alluvial soil, which is found in abundance in the region.

The other options are incorrect because:

• Well-drained laterite soils are not as nutrient-rich as alluvial soils.
• Clayey soils are heavy and can hold too much water, which can suffocate tea plants.
• Sandy soils are too light and do not hold enough water, which can also suffocate tea plants.

In conclusion, the tea plantations of Assam thrive on fertile alluvial soil. This type of soil is rich in nutrients and organic matter, and it is well-drained.