Answer:
C: showing how trends change over time
Step-by-step explanation:
The key feature of this line graph is that it shows how grain production in China changed from 1955 to 1961, increasing steadily over that period of time. Line graphs are useful for illustrating how trends or data points change over a time period.
The graph would not be as useful for the other purposes:
A) The graph does not show percentages, just raw tonnage data.
B) The graph does not show how parts make up a whole, as it only represents one data series (grain production).
D) The graph does not compare information from different sources, as it only shows data on grain production in China.
So in summary, the primary function of this line graph is to show how grain production in China trended over the years from 1955 to 1961, increasing from around 100 million tons to over 200 million tons. Line graphs are well suited to illustrating trends over time, making option C the most appropriate description of what this graph is most helpful for.
The key indicators that point to option C are:
- The x-axis represents years, showing the data is temporal in nature
- The y-axis represents tonnage units, increasing over the time period
- The line steadily rises, illustrating an upward trend