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
Randomisation is useful to eliminate ? 
Select and explain. 
A. Observer bias, B. Confounding factors, C. Patient bias, D. Sampling bias
B: Confounding factors
Answer: B: Confounding factors 
Explanation: Ans. is 'b' i.e., Confounding