The table describes the coordinates of several points on a graph. They form a proportion. What characteristic of the values in the table shows that they form a proportion? A. Both columns include both positive and negative numbers. B. The numbers in the x column increase by a constant amount. C. Each number in the x column relates to only one number in the y column. D. Every number in the x column can be multiplied by the same value to get the number in the y column.