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: Dental
Which of the following demonstrates highest correlation between variables? 
Select and explain. 
A. r = + 0.25, B. r = + 0.5, C. r = - 0.75, D. r = + 2
C: r = - 0.75
Answer: C: r = - 0.75 
Explanation: None