When glass products are made from recycled glass, the resulting products can be equal in quality to glass products made from quartz sand, the usual raw material. When plastics are recycled, however, the result is inevitably a plastic of a lower grade than the plastic from which it is derived. Moreover, no applications have been found for grades of plastic that are lower than the currently lowest commercial grade. Which one of the following is a conclusion that can be properly drawn from the statements above? ['Glass products made from recycled glass are less expensive than comparable products made from quartz sand.', 'Products cannot presently be made out of plastic recycled entirely from the currently lowest commercial grade.', 'It is impossible to make glass products from recycled glass that are equal in quality to the best glass products made from the usual raw material.', 'The difference in quality between different grades of glass is not as great as that between different grades of plastic.']