Answer: Option A. -> True
:
A
Clayey soil has an important characteristic that it can retain water and moisture. Paddy, wheat and gram need a lot of water for their growth. Therefore, clayey soil is suitable for growing cereals like wheat and gram.Clayey is also rich in humus and other minerals which is also ideal for paddy and wheat.
So the statement is true.

Answer: Option A. -> Soil is the base for agriculture.
:
A
Soil is a vital natural resource. It supports the growth of plants and crops by giving nutrients. Agriculture fulfills the food requirement for the survival of human beings. It provides shelter to organisms such as earthworms and many micro-organisms.

Answer: Option C. -> Sandy soil 
:
C
Sandy soil consists of large particles. Interparticle spaces are also very large which prevents the soil from retaining water, making it hard for the roots of plants to establish. This type of soil is the least suited for cultivating crops.

Answer: Option A. -> Soil is made up of different types of components
:
A
The different layers observed is due to the fact that soil is made up of different types of materials all of which have different sizes and weight. The lighter materials float on top and the heavier particles settle at the bottom.

Answer: Option B. -> Weathering and erosion of rocks
:
B
Soil on earth isformed as a result of continuous and long period of constant erosion and weathering of rocks. Large rocks break down to form soil. This is called weathering of rocks. Soil erosion breaks down large particles into smaller soil pieces.

Answer: Option C. -> i - c; ii - d; iii - a; iv - b
:
C
Horizon O is a layer of partially decomposed organic matter lying above topsoil.
Horizon A is the topsoil. It is dark in colour due to the presence of large amount of humus. It makes the soil nutrient rich and fertile. The layer is soft, porous and can retain more water.
Horizon B is the layer below horizon A and has less quantity of humus but at the same time it contains more minerals.
Horizon C is thelayer which is composed of partially eroded small lumps of rocks.

Answer: Option A. -> Clay soil
:
A
$\bullet$ Clay soil is the type of soil that is composed of fine particles.Hence, it has very few air spaces. Unlike sandy soil, it will not flow out of the hand if we hold it in our fist.
$\bullet$Sand particles are quite large. They cannot fit close together, so there are large spaces between them. These spaces are filled with air. So, it has highest air spaces bewteen its particles.
$\bullet$ Loamy soils have particle sizein between those of sandy and clayey soils.So, it has air spaces between those of sandy and clayey soil.
$\bullet$ The rotting dead matter in the soil is called humus.

Answer: Option A. -> The climatic conditions are different in different regions.
:
A
The climatic conditions like wind, rainfall, humidity, amount of available sunlight, etcdetermine the type and soil profile of a particular region.

Answer: Option D. -> Dead remains of plants and animals
:
D
Humus is the lightest layer of soil profile and floats on top of water. It is composed of dead and decomposingremains of animals and plants. Ithelps increase the quality of soil by adding nutrients to it. It makes the soilmore suitable for plant growth.

Answer: Option A. -> True
:
A
Soil provides structural support to plants as roots can firmly hold the soil. It is also responsible for supplying water, nutrients and minerals that are essential for theproper growth of a plant. Themicro-organisms present in soil helps in adding nutrients and minerals to the soil through their microbial actions.