A. The point (2.5, 10) indicates that the cost is $10 for 2.5 pounds of cheese. B. This graph includes decimal values, so it does not show a proportional relationship.
C. This graph line has a constant rate of change and passes through the origin, so it shows a proportional relationship.
D. The constant of proportionality is 1 because the line goes to the right one unit and up one unit.
E. The point (1, 4) indicates that 4 pounds of cheese cost $1.