In data visualization, what does a legend do?

• A. It adds decorative elements to the chart.
• B. It is unnecessary for most charts.
• C. It clarifies which data series is which.
• D. It makes the chart take longer to load.

Answer: (C)

A legend serves as a reference that maps the visual cues—like colors, line styles, or symbols—to the data series in a chart. When multiple series are shown, the legend tells you which color or marker corresponds to which dataset, so you can interpret trends and comparisons correctly. Without it, you might confuse lines or bars and misread the chart. Legends are about clarity and readability, not decoration or performance, which is why the correct choice describes that it clarifies which data series is which.