Which of the following is obtained by joining the midpoints of histogram blocks?

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.