This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Sampling, Subject name: Social & Preventive Medicine
In a study every fouh student is selected in a class while sampling. This is a type of:- 
Select and explain. 
A. Simple random sampling, B. Systematic random sampling, C. Stratified random sampling, D. Cluster random sampling
B: Systematic random sampling
Answer: B: Systematic random sampling 
Explanation: Systematic Random Sampling:- Based on sampling fraction: Every Kth unit is chosen in the population list, where K is chosen by sampling internal. Sampling interval (K) : Total no. of units in population / Total No of units in sample.