(b)The first step before growing crops is preparation of the soil.
So the soil is first prepared to help in better growth of the crops. As we know that roots play a vital role in the proper growth of a plant/crop, so its necessary to make the soil ready before sowing of seeds.
Preparation of soil includes ploughing which gradually loosens the soil so that it can hold nutrients and water. These nutrients and water are transported to the crop through their roots.
Loosening of soil also helps the root to penetrate deep into the soil and help the soil microbes and earthworms to grow in the soil so that they can feed on plant debris(dead roots, leaves, grasses, manure). Their excreta contributes a lot for the nutrition of plants and when they decompose it further contributes to the nitrogen content of soil.