The reason that the chemical/synthetic fertilizers should be replaced by biofertilizers is that the former
are the source of environmental pollution
are expensive
exhaust of valuable energy resources for their manufacture
all of these
As we have already studied in Microbes as Biofertilizers -
plant-growth promoting rhizobacteria- a bacterial microbe
- wherein
they are extremely advantageous in enriching soil fertility and fulfilling plant nutrient requirements by supplying the organic nutrients through microorganism and their byproducts
Hence, the correct option is (d).