Restoration of the original paint colors in Colonial-era rooms has until now relied on the technique of scraping paint in a small area down to the chronological level that represents the paint layer of the Colonial period and then matching the color found at that level. This color was most often the color of putty.

Which of the following, if true, most seriously weakens the validity of the procedure described above?

(A) If the scraping is too deep, a scratch will be made in the surface of the original paint.
(B) In the Colonial period, it was customary to paint all the walls of a room the same solid color.
(C) It is possible to distinguish the paint used in stenciled border designs, such as those used in the Colonial period, from the underlying paint layer.
(D) The original colors were altered over the years by reactions with air, light, and dirt to become putty-colored.
(E) Contemporary paint materials include many that did not exist in Colonial times