Choose the right answer from the four alternatives given below.

Which one of the following is the most widespread and most productive category of soil?

A is correct. Alluvial soil is rich in all nutrients, and is renewed periodically due to flooding. It is intensely cultivated.

B is incorrect. The soils are poor in lime and silica due to leaching. Also, humus is eaten away by bacteria, thus the soil lacks organic matter.

C is incorrect. Black soil lacks phosphorus and potash.

D is incorrect. Forest soils are acidic and have low humus content.