A pie chart is a circular statistical graphic specifically designed to illustrate numerical proportion. The entire circle represents the total value (the "whole"), and it is divided into slices to represent the individual components or categories (the "parts"). The size of each slice is directly proportional to the value of the part it represents, making it the ideal choice for visualizing how individual parts contribute to a whole for a single data series.

B. Bubble chart: This chart type is used to display three dimensions of data, comparing relationships between numeric values, not showing proportions of a total.
C. Line chart: This chart is primarily used to display trends in data over time or ordered categories, showing change rather than composition.
D. Radar chart: A radar chart compares the values of multiple quantitative variables for one or more subjects, which is useful for multivariate comparison, not part-to-whole analysis.

1. Microsoft Corporation. (n.d.). Available chart types in Office. Microsoft Support. Retrieved from https://support.microsoft.com/en-us/office/available-chart-types-in-office-a6187218-807e-4103-9e0a-27cdb19afb90.

Reference Detail: In the "Pie charts" section

the documentation states

"Pie charts show the size of items in one data series

proportional to the sum of the items... Use a pie chart when: You only have one data series. ... None of the values you want to plot are negative. ... Almost none of the values you want to plot are zero values. ... You have no more than seven categories

all of which represent parts of the whole pie."

2. Heer

J.

& Agrawala

M. (2012). Lecture 4: Chart Types. University of Washington

CSE 442: Data Visualization course materials.

Reference Detail: The lecture slides on "Part-to-Whole (Proportions)" explicitly list Pie Charts and Stacked Bar/Area Charts as the primary methods for this type of data visualization

reinforcing the pie chart's role in showing contributions to a total.

3. Carnegie Mellon University Libraries. (n.d.). Data Visualization: Chart Types. LibGuides.

Reference Detail: In the section on "Composition" charts

the guide describes Pie Charts as being used to "show parts-of-a-whole." It clarifies that they work best with a small number of categories. This aligns with the function described in the question.