This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: DNB 2018, Subject name: Social & Preventive Medicine
What is the recommended level of chlorine in Swimming pool? 
Select and explain. 
A. >0.5 mg/L, B. >0.8 mg/L, C. >1 mg/L, D. >5 mg/L
C: >1 mg/L
Answer: C: >1 mg/L 
Explanation: Residual chloride levels in: (i.e. after the contact period of one hour) Drinking water- >/= 0.5 mg/L or ppm Swimming pools- >/= 1.0 mg/L To kill Cyclops in Drinking water - >/= 2.0 mg/L Residual chlorine level can be measured using chloroscope/ Ohotoluidine test.