The correct answer is option 'C', which states that the bar diagram showing an aggregate of values and its parts is called a component bar diagram.

A component bar diagram is a graphical representation used to display the relationship between a whole and its parts. It is also known as a stacked bar chart or a segmented bar graph. In this type of diagram, each bar represents the total value or aggregate, and the different segments within the bar represent the individual components or parts.

Here is a detailed explanation of the answer:

I. Definition of a component bar diagram
- A component bar diagram is a type of bar chart that visually represents the composition or breakdown of a whole into its constituent parts.
- It is particularly useful when comparing the relative sizes or proportions of different categories within a larger category.

II. Structure of a component bar diagram
- The diagram consists of a set of vertical or horizontal bars, each representing the total value or aggregate.
- The length or height of the bars represents the magnitude of the aggregate.
- The bars are divided into segments or sections, with each segment representing a specific component or part.
- The length or height of each segment within the bar represents the magnitude or proportion of that component.

III. Purpose and use of a component bar diagram
- A component bar diagram is commonly used in business, economics, finance, and other fields to visually present data that involve a whole and its parts.
- It helps in understanding the composition of a whole and the relative contribution of each component.
- It enables easy comparison and analysis of the proportions or percentages of different components within the aggregate.

IV. Example of a component bar diagram
- Let's consider a scenario where the total revenue of a company is represented by a bar, and the different segments within the bar represent the revenue generated from various product categories.
- Each segment's length within the bar would represent the proportion of revenue contributed by that product category.
- The component bar diagram would provide a clear visual representation of the revenue composition and the significance of each product category.

In conclusion, a component bar diagram is a specific type of bar chart used to represent the composition or breakdown of a whole into its constituent parts. It is a valuable tool for visually displaying and analyzing data related to aggregates and their components.