Final answer:
The best option for representing percentages of a whole in a Microsoft Excel graphical report is a Pie chart, as it clearly shows how the whole is divided into relative parts.
Step-by-step explanation:
When working with an application such as Microsoft Excel to generate graphical reports, the BEST for data that represents percentages of a whole is a C) Pie chart. A pie chart is designed to show the proportion of each category relative to the entire dataset, with each slice representing a percentage of the whole. This format makes it easier for viewers to understand the relative sizes of each part in comparison to the others.
While bar charts effectively display comparisons between different groups or changes over time, pie charts are exceptionally suited for illustrating how a single total is divided among different categories. It's essential that the pie chart is designed carefully, with legible percentages and clearly distinguishable colors for each category to ensure that it conveys the information effectively. If there are too many categories, a pie chart can become cluttered, so it is ideal to use it when there are fewer slices to maintain clarity.