Authentic economic data supplied on CDs is prepared and released by laboratories, research centres and government agencies — option (c).

In any study of the Gujarat HSC / GSEB Class-12 Commerce Economics course, the first requirement for drawing diagrams and graphs is a reliable data source. Economic information distributed in digital form (CDs, online databases, official portals) is compiled by organisations that have the capacity and authority to collect large-scale statistics — namely research laboratories, research centres and various government departments (such as the CSO, RBI, census organisation, etc.).

Private publishers, schools or individuals may reproduce such data, but they are not the primary agencies that generate and certify it. Using data from an authentic institutional source ensures accuracy and comparability.

Among the given options only the pictogram is a diagram; the rest are graphs — option (a).

In statistics the presentation of data is broadly split into diagrammatic presentation and graphic presentation. Diagrams include bar diagrams, pie diagrams, pictograms and cartograms — they communicate data through shapes, pictures or symbols and are mainly for the common reader.

A histogram, frequency polygon and frequency curve, on the other hand, are drawn on graph paper using axes (X and Y) to show a frequency distribution, so they are classified as graphs, not diagrams.

Hence a pictogram, which shows data with small pictures/symbols, is the only diagram in the list.

Formula of a pie diagram: Component angle = (Component value / Total value) × 360°.

A pie (circle) diagram presents the components of a total as slices of a circle. Since a full circle has 360°, each component is allotted an angle in proportion to its value relative to the total.

The formula used to find the angle of each slice is:

Angle of component = (Value of that component ÷ Sum/Total of all values) × 360°

When every component's angle is calculated this way and the slices are drawn, the circle is fully divided among the parts.

A diagram is drawn for a discrete/discontinuous distribution — option (a). Diagrams suit data grouped into distinct, separate categories; continuous data are shown by graphs.

In the presentation of statistical data (a core topic in GSEB Class-12 Commerce Economics), we distinguish between two visual tools:

• Diagrams (bar diagrams, pie diagrams, pictograms) are used for discrete or discontinuous data — values that fall into separate, distinct categories such as production of different crops, population of different states, or sales in different years.
• Graphs (line graphs, histograms, frequency curves) are used for continuous data that flow without breaks, such as time-series values.

Since the question asks the type of distribution for which a diagram is drawn, the answer is the discrete/discontinuous type. 'Ideal' and 'skewed' describe the shape of a distribution, not the diagram-vs-graph choice.

The correct option is (C) Divided Bar Diagram — bars sharing a common base and common variable, each split into parts, form a divided (component) bar diagram.

In a Gujarat HSC / GSEB Class-12 Commerce Economics diagram, a simple bar diagram draws one bar of a single height for each item, so there are no divisions inside a bar. A divided (sub-divided or component) bar diagram takes each total and splits its single bar into segments, one segment per component, all measured on the same scale and drawn on the same base line. This lets a reader compare both the totals (full bar heights) and the shares of each component across items. A frequency polygon is a line graph joining class mid-points, not a bar chart at all.

In a pie diagram the angle at the centre for each component is (component value ÷ total value) × 360°.

A pie (circular) diagram, used in GSEB Class-12 Economics diagrammatic presentation, shows how a total is divided among its parts. Since the whole circle is $360^\circ$, each component is given a slice whose central angle is proportional to that component's share of the total.