Red soils are found in the southern parts of Bihar and are characterized by their:

The correct answer is: c) Richness in iron and aluminum oxides.

Red soils are found in the southern parts of Bihar and are characterized by their high content of iron and aluminum oxides. These oxides give the soil its characteristic red color. Red soils are also known for their poor drainage and low fertility.

Option a) is incorrect because red soils are not typically dark in color. Option b) is incorrect because red soils do not typically have a high clay content. Option d) is incorrect because red soils do not typically have a waterlogging tendency.