The quantity of water soil can retain after flowing down of the gravitational water is called its filled capacity or water holding capacity. Its depends on chemical composition of the sol which means types of ions present and hence pH of the soil . Size of sol particles and their aggregation form pores in soil. Large pores take part in percolation of water in the soil but small pores hold water by capillarity. 

We know that the growth of plants in the soil requires the presence of certain substances in it. This includes water and also nutrients present inside the soil.

Cotton crops are best grown in black soil. It is also known as black cotton soil. Black soil contains a very high proportion of calcium and magnesium and so cotton plants can obtain their necessary requirements. 

Fungi and Bacteria grow mostly in top soil. As Fungi is a saprophyte it feeds,on decay and some bacteria decomposes the fallen leaves into manures.

(c) The amount of water retained by a unit weight of undisturbed soil after complete drainage under controlled coniditions is called field capacity or holard.

Explanation: Silt is granular material of a size somewhere between sand and clay, whose mineral origin is quartz and feldspar. Silt may occur as a soil or as sediment mixed in suspension with water (also known as a suspended load) in a body of water such as a river. Silty soil is usually more fertile than other types of soil, meaning it is good for agriculture.

Colluvium is a type of parent material that moved down slope due to gravitational forces (in some cases water may play a role in initiation of the movement). Colluvium is heterogeneous, unsorted material of all particle sizes (from boulders to clay) with relatively little abrasion to round the particles. Consequently, colluvium consists of very sharp, angular rock fragments accumulated at the base of steep slopes.
Aeolian soil : A type of soil that is transported from one place to another by the wind.
Alluvium  is loose, unconsolidated (not cemented together into a solid rock) soil or sediments, which has been eroded, reshaped by water in some form, and redeposited in a non-marine setting.
Glacial soil  Unsorted, non-stratified glacial deposits consisting of clay, silt, sand, and boulders transported and deposited by glacial ice.

Colluvium is a type of parent material that moved down slope due to gravitational forces. Colluvium is heterogeneous, unsorted material of all particle sizes (from boulders to clay) with relatively little abrasion to round the particles.

Black soil is used to make matkis and surrahis. This is because it provides proper support due to air spaces between their particles. It can also retain water for a long period of time. Along with this, it can withstand a large amount of climatic change also.

Laterite is a soil layer, that is rich in iron oxide and derived from a wide variety of rocks weathering under strongly oxidizing and leaching conditions. It forms in tropical and subtropical regions, where the climate is humid. When the velocity of running water decreases the heaviest particles are deposited on a riverbed. The finest particles (gravel, silt, sand, and clay) are deposited at the mouth of the river, forming a delta made of alluvial soil. 

Alluvial soils are most extensive soil. It is formed due to deposition of the rivers brought down from the upper course of the river. It is found on the combined plain land of the Indus and the Ganga-Brahmaputra rivers which includes Punjab, Haryana, U.P., Bihar and West Bengal. The deltaic alluvium is found in deltas of the Ganga-Brahmaputra, Godavari, Mahanadhi and Kaveri rivers. The coastal alluvium is found in coastal sides of Peninsular India - called riverine soils it is originally found in river basins.

Dead plants and animals are degraded in soil by decomposing bacteria and fungi. The material formed after this decomposition activity is called humus. Humus is very rich in nutrients and black in color. Hence topsoil is the darkest. Greater the amount of humus more is the soil productivity. Thus the correct answer is option A.

Deep black soil has a high proportion of clay and humus and high retentivity of moisture and thus are very productive for cultivation of important crops like cotton, wheat, jowar, linseed, castor, sunflower, millets, rice and sugarcane.

Black soil is the fertile soil present in India. It is abundantly found in Haryana, Maharashtra and Uttar Pradesh. The black colour of the soil is due to the presence of iron, aluminium and humus. This type of soil is most suitable for the cultivation of grains, vegetables and cotton.

Red soil is a mixture of loamy and yellow soils. Its red colour is due to the presence of abundant iron oxide. About two-thirds of Tamil Nadu has Red soil.It is suitable for the cultivation of tobacco, vegetables and paddy. Black soil is the fertile soil present in India. It is abundantly found in Haryana, Maharashtra and Uttar Pradesh. The black colour of the soil is due to the presence of iron, aluminium and humus. This type of soil is most suitable for the cultivation of grains, vegetables and cotton

Laterites are formed by leaching of parent sedimentary rocks. They  are rich in Al and Fe and are found in wet and hot tropical areas. The color of the soil is rusty red due to high Fe content.

Red soil is a mixture of loamey and yellow soils. It is suitable for the cultivation of tobacco, vegetables and paddy.

Black soil is dark brown or black colour soil. The black colour is due to organic matter and clay content. Such soils are compact with good hydration, but little aeration; chemically they are very fertile, because of rich mineral content. Rich mineral content of black soils is due to clay, which adsorbs minerals on its surface. Clay and humus produce colloidal complex for holding water and ions and forming soil crumbs.

(b) Black soil predominantly with clay and humus. This soil is very fertile because most of minerals are present in it. 

Laterite is a soil and rock type rich in iron oxide. It is reddish in colour. 

Soil texture refers to the relative proportion of particles or it is the relative percentage by weight of the three soil separates i.e., sand, silt and clay or the size of soil particles. According to the International system, 

Explanation: These burrows create pores through which oxygen and water can enter and carbondioxide can leave the soil. Earthworm casts (their faeces) are also very important in soils and are responsible for some of the fine crumb structure of soils.

Chernozem is the black colored soil which is known for being rich in humus. This is the richest soil in the world and used for the cultivation of the cereals. Black soil is rich in calcium carbonate and iron. This soil also contains the lime, potash, aluminum, etc. Laterite soil contains the bauxite which is the ore of the aluminum. Terra Rossa is the red clayey soil. the soil formed from the limestone and is used for the production of the vine plants.