The correct option is C manure
Answer is C.
The digested slurry which comes out of the biogas plant is more important that the gas itself which is used for cooking purposes. It is a by-product obtained from the bio-gas plant after digestion of dung or other biomas for generation of methane rich gas. It supplies essential nutrients, enhances water holding capacity and soil aeration, accelerates root growth and inhibits weed seed germination.