The correct option is A Manure
Manures are organic substances formed by the decomposition of animal excreta and plant wastes. They provide nutrition to plants. They are natural and contain no chemicals. Thus, they do not decrease the fertility of the soil. Meanwhile, ammonia, superphosphate and ammonium sulphate are the constituents of chemical fertilisers. Excessive usage of these fertilisers can damage the soil in many ways, and can lead to soil infertility.