Final answer:
A Line chart is the best option for graphical representation of data that changes over time at intervals, as it clearly shows trends and progressions.
Step-by-step explanation:
When working with an application to generate graphical reports for data that changes over time at intervals, a Line chart (A) would work BEST. Line charts efficiently show trends by connecting individual data points with lines, making it easier to track changes and progressions over time. This is particularly useful for time series data, such as monitoring the unemployment rate or sales figures across different months or years. Comparatively, pie charts are better for showing composition of a whole at a single point in time, and bar charts can be useful for comparing quantities across different categories. However, for continuous data that changes over time, the clarity and simplicity of a line chart often make it the superior choice.