This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
[{'content': 'Which of the following statement regarding normal microbial flora present on the skin and mucous membranes is true? \nSelect and explain. \nA. It cannot be eradicated by antimicrobial agents, B. It is absent in the stomach due to the acidic pH, C. It establishes in the body only after the neonatal period, D. It does not have any protective functions', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Normal microbial flora are more or less constant for each species and are broadly classified as residents and transients. Residents constitute a constant population which cannot be completely removed permanently, while transient organisms vary from time to time and are not permanent. Antimicrobials cannot remove the normal flora organisms completely, only transient removal is possible. Ref: Textbook of Microbiology and Immunology By Parija, Pages 647-9; Textbook of Microbiology By Ananthanarayan, 6th Edition, Page 555', 'role': 'assistant'}]