Answer:
The correct answer is A) human microbiome
Explanation:
Human microbiome consists of all the micro-organism that is regularly present on or in the human body. The number of microorganisms present in our body is way more than the number of cells our body is made up of. Human microbiome does not include pathogenic microbes.
The human microbiome is very much important for our survival. The gut microbiota helps in digestion, improving the immune system, production of vitamins, protecting us from opportunistic pathogens, etc. So the correct answer is A.