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
Certain species are invariably found at certain locations, this phenomenon is called as: 
Select and explain. 
A. Resident flora., B. Transient flora., C. Tissue tropism., D. None
C: Tissue tropism.
Answer: C: Tissue tropism. 
Explanation: Certain septicies are invariably found at certain locations. This phenomenon is called Tissue tropism. The normal microbial flora which are present constantly are called resident floral and which change frequently are called Transient flora