Final answer:
The option that allows John to include a guide displaying the names of the data series on his Pivot chart is c) Legend.
Step-by-step explanation:
John has created a Pivot chart and would like to include a guide that displays the names of the series of data included on the chart. The option that would allow him to do this is c) Legend. A legend is a key located on the chart that identifies each line on a line graph, or data series on other types of charts, by color or pattern. It is useful for providing information at a glance about what each data series represents without needing to look back at the data table. Legends are essential when a chart contains multiple lines or data series, as it helps differentiate them for better data analysis and understanding. Data labels are the direct labeling of data points, axis titles label the individual axes, and a trendline is a line added to a graph that shows the trend in the data and helps to predict future values.