Bar Graph
Bar graphs can be used to compare changes over the same period of time for different entities such as the given case has two plants. The bars can be plotted vertically or horizontally. A vertical bar chart is sometimes called a line graph. As Dan is calculating the progress of two different plants over continuous period of time of sunflower seedling for two different fertilizers so he needs a bar graph for it.
Answer:
Option A, Bar graph
Explanation:
A bar graph is the best tool to represent and compare changes between a given set of group during a certain time period of observation.
A pie chart is more useful while comparing the parts of a whole. Data table is useful when there are several factors of comparison (unlike the case here where only growth in centimeters is being compared). Venn diagram is useful in case of data related to a set and its subsets.
Thus, among all given options bar graph will be the most appropriate way of representing total growth of all plants in centimeters.
