Which sentence best introduces a chart describing changes over a period?

• A. The chart illustrates how the figures for X varied over the period from Y to Z.
• B. The chart shows weather data.
• C. The chart compares two datasets.
• D. The chart is not informative.

Answer: (A)

When a chart shows changes over time, the best opening clearly states what is being measured, that values change, and the exact period covered. This sentence does that by saying the chart illustrates how the figures for X varied over the period from Y to Z. It immediately tells the reader the subject (figures for X), the action (varied), and the time frame (from Y to Z), which prepares the reader to follow the subsequent data. The other options are less effective because they are either too vague about changes over time or describe a different chart purpose (weather data without a time frame, a comparison of two datasets, or no information at all).