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 sampling method is used in assessing immunization status of children under an immunization program 
Select and explain. 
A. Quota sampling, B. Multistage sampling, C. Stratified random sampling, D. Cluster samping
D: Cluster samping
Answer: D: Cluster samping 
Explanation: None