A bar chart or bar graph is a chart or graph that presents categorical data with rectangular bars with heights or lengths proportional to the values that they represent. The bars can be plotted vertically or horizontally. A vertical bar chart is sometimes called a line graph.

The correct answer is option 'D' - (a) or (c). Let's break down the explanation for this answer.

Horizontal bar diagrams, also known as horizontal bar charts or bar graphs, are a type of visual representation used to display data in a horizontal format. They consist of rectangular bars of different lengths, with each bar representing a specific category or variable. The length of the bar corresponds to the value or magnitude of the data being represented.

Now, let's look at each option mentioned and examine whether it applies to the use of horizontal bar diagrams:

a) Qualitative data: Qualitative data refers to non-numerical information or attributes that cannot be measured on a numerical scale. Horizontal bar diagrams are typically not used to represent qualitative data, as they are more suitable for quantitative data that can be measured and compared. Therefore, option 'a' is incorrect.

b) Data varying over time: Horizontal bar diagrams can indeed be used to represent data that varies over time. In this case, each bar would represent a specific time period, and the length of the bar would correspond to the value or magnitude of the data for that particular time period. For example, if you were representing the sales figures of a product over different months, you could use a horizontal bar diagram to show the sales for each month. Therefore, option 'b' is correct.

c) Data varying over space: Horizontal bar diagrams can also be used to represent data that varies over space. In this case, each bar would represent a specific location or geographical area, and the length of the bar would correspond to the value or magnitude of the data for that particular location. For example, if you were representing the population of different cities, you could use a horizontal bar diagram to show the population for each city. Therefore, option 'c' is correct.

Since both options 'b' and 'c' are correct, the correct answer is option 'D' - (a) or (c). Horizontal bar diagrams can be used for data varying over time or data varying over space.

D