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
It is true regarding the normal microbial flora present on the skin and mucous membranes that ? 
Select and explain. 
A. 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. The flora in the small bronchi is similar to that of the trachea
A: It cannot be eradicated by antimicrobial agents
Answer: A: It cannot be eradicated by antimicrobial agents 
Explanation: Ans is 'a' i.e., It cannot be eradicated by antimicrobial agents . The normal microbial flora are more or less constant for each species and are broadly divided into residents and transients. The former constitute a constant population which cannot be completely removed permanently. - Ananthanarayan 7'''/e 599 . Because of low pH of stomach, it is viually sterile except soon after eating - Ananthanarayan 71/4 601 . With in 4-24 hours of bih an intestinal flora is established - Ananthanarayan r/e 600 . In the pharynx and trachea, flora is similar to that of mouth, while smaller bronchi and alveoli are normally sterile - Ananthanarayan 7th/e 600