What type of graph is the best display of percentage of parts composing a whole?

A pie chart is the best display for showing the percentage of parts composing a whole. It visually represents each category as a slice of the pie, making it easy to compare proportions at a glance. This format is particularly effective when you have a limited number of categories, as it emphasizes the relationship of each part to the total. For more complex data with many categories, a stacked bar chart could also be considered.