Answer: Sample Response: You can tell a graph is proportional if the points form a single line and that line passes through the origin. The relationship between input and output figures will also remain the same throughout.
Explanation: It was the sample response but if you don't want it to look the same just be sure to include these ideas:
-The points will form a straight line.
-The straight line will pass through the origin.
-The ratio of input and output is always the same.
Good luck!