Read the below questions carefully and answer the given questions:A combined mixture of light, loose and unstructured rocky shreds and fine-grained bacteria found on the earth’s surface is called soil which has the power to give rise to plants. Deposition of this mixture is found in deep layers ranging from 15-30 cm to several metres. But the soil scientist is divided into three layers called A, B and C respectively, depending on the depth and quantity of soil colour, texture, size of particles etc. Due to the high quantity of humus in ‘A’ Horizon soils, they begin to turn black. But due to being situated in the zone of leaching on this layer, the minerals dissolve and go down and the colour starts to turn dark black. The colour of sub-layer with ‘B’ Horizon under this layer is brown due to the mineral matter leaking from the top layer. But the aihount of humus in it decreases. Below this layer, a layer of ‘C’ Horizon soil is found in which the substances separated from the above rocks do not have any special change and later go to the main base rock. The colour of this sub-rocky surface is grey or light brown,(a) Describe the definition of soil.(b) What is the contribution of primary rocks in the birth of soil?