You plan to generate a line chart to visualize and compare the last six months of sales data for two departments. You need to increase the accessibility of the visual. What should you do?

While abbreviations can save space, they can decrease accessibility if users do not understand them, and they do not directly address visual differentiation for multiple series.

Configuring a unique marker for each series in a line chart greatly improves accessibility, particularly for users with color vision deficiency. It allows them to differentiate between series even if they cannot distinguish between the colors used.

While using distinct colors is generally good practice, it is insufficient for users with color vision deficiency, as they may not perceive the colors as distinct. Unique markers provide an additional, non-color-dependent differentiator.

Moving important information to a tooltip can hide critical details, making the visual less accessible for quick comprehension, and it doesn't address the primary issue of differentiating series for users with visual impairments.