Final answer:
Having a dog increases microbial diversity, enriching the human microbiome with new species and potentially enhancing the protective effects against pathogens. The correct option is C.
Step-by-step explanation:
Having a dog can affect the microbiota in a positive way. Research indicates that exposure to pets, especially dogs, can lead to an increase in microbial diversity. This increase in microbial diversity within human habitats has been associated with various health benefits, including improved immune function and reduced incidence of allergies.
The presence of dogs in the household tends to introduce a variety of microorganisms from the environment. These microbes may be transferred to humans directly through contact with the pet or indirectly through the modification of the home's microbial community.
Consequently, being in close contact with a dog can enrich the human microbiome by adding new microbial species and increasing the abundance of others, potentially enhancing the protective effects of our resident microbiota and decreasing our susceptibility to pathogenic invasions. Therefore, the correct answer is (c) It increases microbial diversity.