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
[{'content': 'Proposed guideline values for Radioactivity in Drinking water is \nSelect and explain. \nA. Gross a activity 1.0 Bq/L and Gross b activity 10.0 Bq/L, B. Gross a activity 1.0 Bq/L and Gross b activity 0.1 Bq/L, C. Gross a activity 0.1 Bq/L and Gross b activity 1.0 Bq/L, D. Gross a activity 10 Bq/L and Gross b activity 1.0 Bq/L', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Key guideline aspects of WHO recommended drinking water quality: –\nColour < 15 true colour units (TCU)\nTurbidity < 5 nephlometric turbidity units (NTU)\npH: 6.5 – 8.5\nTotal dissolved solids (TDS) < 600 mg/litre\nZero pathogenic microorganisms\nZero infectious viruses\nAbsence of pathogenic protozoa and infective stages of helminthes\nFluorine < 1.5 ppm (0.5 – 0.8 ppm: Optimum level)\nNitrates < 50 mg/litre\nNitrites < 3 mg/litre\nGross alpha radiological activity < 0.5 Bq/litre (New Guideline — WhO)\nGross beta radiological activity < 1.0 Bq/litre (New Guideline — WhO).', 'role': 'assistant'}]