Jenny places a strip of pH paper into a solution. When she removes the pH paper, it has turned yellow-green.
What should Jenny do next to determine the pH of her solution?
A. use a different testing method because the pH paper should not change colors
B. place the pH paper into a machine that reads the pH of the solution
C. compare the pH paper's color with the color of pH paper from another solution
D. compare the pH paper's color with a chart of colors and pH ranges