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
Occurrence of malocclusion in given population is best described as: 
Select and explain. 
A. Prevalence rate, B. Incidence rate, C. Morbidity, D. Probability
A: Prevalence rate
Answer: A: Prevalence rate 
Explanation: None