This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Environment and health, Subject name: Social & Preventive Medicine
Strength of sewage is - 
Select and explain. 
A. E. Coli count, B. Suspended solids, C. Nitrate, D. Coliform count
B: Suspended solids
Answer: B: Suspended solids 
Explanation: Sewage is waste water from community,containing solid and liquid excreta derived from houses ,street, yards. The strength of sewage is indicated by A)biochemical oxygen demand B)chemical oxygen demand C)suspended solids Amount of suspended solids in domestic sewage varies from 100 -500 p.p.m.(mg/L) If the amount is 100 mg/L- weak If amount is 500 mg/L- strong. Parks textbook of preventive and social medicine.K Park. Edition 23.Pg no: 763