Definition of Key
In the graph shown, the key is given to the right of the graph to notify us which line graph corresponds to which hitter. The key here is important, because otherwise we wouldn't be able to answer any question comparing the two hitter's performance.
Solved Example on Key
Find the number of keys in the graph.
Correct Answer: B
Step 1: From the graph, it is clear that there are two categories boys and girls.
Step 2: So, the number of keys = 2.