What is the definition of taxonomy?

If all prokaryotes on earth suddenly vanished, which of the following would be the mostlikely and most direct result? a) the number of organisms on earth would decrease by 10—20%.b) human populations would thrive in the absence of disease.c) bacteriophage numbers would dramatically increase.d) the recycling of nutrients would be greatly reduced, at least initially.e) there would be no more pathogens on earth.