The correct option is C (a), (b) and (c) are true
∙ Long term high yielding capacity of soil depends on the availability of nutrients in the soil, making it fertile and also the physical, chemical and biological characteristics of soil.
∙ To improve soil health and productivity biofertilisers were used, these do not have nutrients in them like organic manures. They synthesise nutrients from environment and soil. These are also called farmer friendly fertilisers.
∙ Panchagavya is a natural manure helpful to grow crop with higher yielding. It is also used as food for hens and fish in ponds.