Answer:
A. to show the relationship of parts to a whole
Explanation:
A pie chart uses "pie slices" to show relative sizes of data. It forms a circular chart in which each proportion of the "pie" is a percentage of the whole, the total value of them always is 100%. In this type of chart, compared data is easily understanded as it is presented in a simple way. Remeber that it is usually used when there are few portions of the "pie" as the comparison is clearly visible. As the "pie slices" increase it becomes more difficult to compare and read.
