Detailed Explanation:

A run chart is the best tool to illustrate trends over time, as it displays changes in data across a specific period.

Option D: Run chart

A run chart shows data points plotted in chronological order, making it ideal forobserving trends or patterns, such as increases or decreases in medication errors over time.

Option A: Scatter diagram

Scatter diagrams show the relationship between two variables but do not display changes over time.

Option B: Pie chart

Pie charts represent proportions within a single point in time, unsuitable for illustrating trends.

Option C: Histogram

Histograms show frequency distributions but do not effectively illustrate trends over time.