Which of the following is a function of the bacterial flora?

• A. Directly causing all human diseases
• B. Production of antibodies against all viruses
• C. Synthesis of certain vitamins such as vitamin K
• D. Breaking down host DNA for energy

Answer: (C)

Verified step by step guidance

1. Understand what bacterial flora refers to: it is the community of microorganisms, mainly bacteria, that live in and on the human body, often in symbiotic relationships.
2. Recall the roles of bacterial flora, which include aiding digestion, synthesizing vitamins, protecting against harmful pathogens, and stimulating the immune system.
3. Evaluate each option by comparing it to known functions of bacterial flora: they do not directly cause all human diseases, nor do they produce antibodies (which are made by the immune system), and they do not break down host DNA for energy.
4. Identify that one well-known function of bacterial flora is the synthesis of certain vitamins, such as vitamin K, which is essential for blood clotting and is produced by bacteria in the gut.
5. Conclude that the correct function of bacterial flora among the options given is the synthesis of certain vitamins such as vitamin K.