Which of the following statements, if true, would most seriously weaken the claim made above? A. An increase in the price of cardboard containers would not necessarily increase the retail price of items packed in these containers. B. The cost of lumber is a major determinant of the cost of cardboard containers. C. There has been a recent increase in demand for cardboard containers. D. Manufacturers of cardboard containers face increasingly stiff competition from manufacturers of plastic containers. E. Before Company X bought Company Y. Company X had consistently set the prices of its cardboard containers below the prices set by Company Y.