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
[{'content': 'Which of the following is not true about non-randomized trials? \nSelect and explain. \nA. Approach of comparability is high, B. Degree of comparability is high, C. The experiment can serve as its own control or can utilize a natural control, D. Several trials may be needed before evaluation is considered conclusive', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Non-randomized trials ( i.e. Those depaing from strict randomization for practical purposes but in such a manner that non-randomization does not seriously affect the theoretical basis of conclusions ( refer pg 81, park 23 rd edition)', 'role': 'assistant'}]