Suggest a suitable word for each of the following statements.
(a) Chemicals added to food to prevent the growth of microorganisms.
(b) Nitrogen-fixing microorganisms present in the root nodules of legumes.
(c) The agent spreads pathogens from one place to another.
(d) Chemicals which kill or stop the growth of pathogens.
(a) Preservatives:
(b) Rhizobium:
(c) Carrier/Vector:
(d) Antibiotics: