The human body has a large population of bacterial cells; approximately as many as our eukaryotic (human) cells. bacteria coat our skin, gut, and mouth. also present are protists, archaeans, and viruses. collectively, these organisms are our microbiota. you decide to follow the development of the human gut microbiota over time by sampling the solid waste (feces) of infants from birth to 24 weeks old. which of the following set-ups minimizes the sources of variation in your observational study?