Microbes have shaped human history by a. being the causative agents of human epidemics. b. being important in the production of certain food products. c. playing important roles in the geochemical cycling of many elements. d. All of these answer choices are correct.

The correct answer is d. All of these answer choices are correct.

Explanation:

Microbes are present almost everywhere in the world. They are an important part of the earth and human history. They have shaped human history in many different ways. Microbes had been a causative agent of human epidemics which affected a large human population in the past.

From ancient times microbes are used by humans in their food like alcohol production, production of fermented foods, etc. Microbes are an important part of the ecosystem because play an important role in the recycling of nutrients. So the correct answer is D.