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
The response which is graded by an observer on agree or disagree continuum is based on? 
Select and explain. 
A. Visual analogue scale, B. Guttman scale, C. Likert scale, D. Adjective scale
B: Guttman scale
Answer: B: Guttman scale 
Explanation: None