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
Venturimeter is used to measure 
Select and explain. 
A. Air velocity, B. Size of suspended particles in the air, C. Bed resistance in a slow sand filter, D. SO2 content in the atmosphere
C: Bed resistance in a slow sand filter
Answer: C: Bed resistance in a slow sand filter 
Explanation: None