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
[{'content': 'Chlorine demand of water determined by - \nSelect and explain. \nA. Horrocks apparatus, B. Chloronometre, C. Berkefield filter, D. Doble Pot', 'role': 'user'}, {'content': 'Answer: A \nExplanation: 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)', 'role': 'assistant'}]