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
Which of the following is obtained by joining the midpoints of histogram blocks? 
Select and explain. 
A. Pictogram, B. Frequency polygon, C. Bar cha, D. Pie cha
B: Frequency polygon
Answer: B: Frequency polygon 
Explanation: 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.