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
Hardness of drinking water should be: 
Select and explain. 
A. Less than 1, B. 3-Jan, C. More than 3, D. More than 6
B: 3-Jan
Answer: B: 3-Jan 
Explanation: 3-Jan