This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Biostatistics, Subject name: Social & Preventive Medicine
Strong correlation is signified by a correlation coefficient of ? 
Select and explain. 
A. Zero, B. 1, C. Less than 1, D. More than 1
B: 1
Answer: B: 1 
Explanation: .