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
Chlorine demand of water determined by - 
Select and explain. 
A. Horrocks apparatus, B. Chloronometre, C. Berkefield filter, D. Doble Pot
A: Horrocks apparatus
Answer: A: Horrocks apparatus 
Explanation: Horrock &;s water testing apparatus is designed to find out the dose of bleaching powder required for disinfection of water Contents 6 white cups One black cup with a circular mark inside 2 metal spoons 7 glass stirring rods One special pipette Two droppers Starch-iodine indicator solution Instruction folder (refer pgno:729 park 23rd edition)