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: Social & Preventive Medicine
All of following comes under random sampling method except 
Select and explain. 
A. Simple random sampling, B. Quota sampling, C. Stratified sampling, D. Cluster sampling
B: Quota sampling
Answer: B: Quota sampling 
Explanation: None