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: Social & Preventive Medicine
Minimum Brick wall thickness of septic tank should be? 
Select and explain. 
A. 2 inches, B. 9 inches, C. 18 inches, D. 25 inches
B: 9 inches
Answer: B: 9 inches 
Explanation: Ans. is 'b' i.e., 9 inches"Wall built out of brick should not be less than 200 mm thick and should be plastered to a minimum thickness of 12 mm inside and outside with cement moar not weaker than 1:3; where are built out of the stone masonary.A septic tank is usually provided with brick wall in which cement moar thick and the foundation floor is of cement concrete 1:2:4.