What best describes the visual trend of data represented in line graphs?

Line graphs are specifically designed to illustrate how values change over time, making them especially effective for displaying trends. Each point on a line graph corresponds to a data value at a certain time, and the lines connecting these points showcase the movement or fluctuation of values throughout the specified period. This visual representation allows viewers to easily identify trends such as increases, decreases, or cyclical patterns in data.

The other options do not capture this defining characteristic of line graphs. Static representations of values typically convey fixed information without showing dynamics. Comparisons of groups, while possible with line graphs, are more commonly associated with bar charts where differences between categories can be more clearly seen. Lastly, the distribution of percentages is better represented using pie charts or histograms, which show how data is divided into parts rather than how it changes over time. Thus, the ability of line graphs to portray change over a duration distinctly identifies option C as the best description.