This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epidemiology, Subject name: Social & Preventive Medicine
What is the method of sampling in which the units are picked up at regular intervals from the universe? 
Select and explain. 
A. Simple random sampling, B. Systematic random sampling, C. Stratified random sampling, D. Snow ball sampling
B: Systematic random sampling
Answer: B: Systematic random sampling 
Explanation: Systematic sampling is a type of probability sampling method in which sample members from a larger population are selected according to a random staing point but with a fixed, periodic interval. Ref: 25th edition, Park's Textbook of Preventive and Social Medicine, Page no. 913