Detailed Explanation:
To display a trend over time, a line graph is the best choice as it connects data points sequentially, showing the direction and pattern of change.
Option C: Line graph
Line graphs effectively display trends, helping viewers see how a variable changes over time.
Option A: Pie chart
Pie charts are used for showing proportions at a single point in time.
Option B: Pictogram
Pictograms display data using symbols, which are not suitable for trends.
Option D: Frequency distribution
Frequency distributions summarize data points but do not illustrate trends over time.
References:
Line graphs are a standard tool for trend analysis, as recommended in data visualization techniques covered in CPHQ and healthcare quality resources.