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
[{'content': 'Which of the following is obtained by joining the midpoints of histogram blocks? \nSelect and explain. \nA. Pictogram, B. Frequency polygon, C. Bar cha, D. Pie cha', 'role': 'user'}, {'content': "Answer: B \nExplanation: In a Pie cha, the area inside each segment is representative of a fixed percentage of the total. In case of Bar cha the length of the bar is propoional to the magnitude to be represented. A frequency polygon is a diagrammatic representation of a frequency distribution obtained by joining midpoints of histogram blocks. Ref: Park's Textbook of Preventive Medicine, 17th Edition, Page 610.", 'role': 'assistant'}]