Environmental activist groups, which clean up waste left on beaches, in parks, and along the side of the road, report that glass bottles make up an ever-increasing percentage of waste they remove. It is clear that attempts to decrease the amount of glass that people litter are failing. Which one of the following, if true, most seriously weakens the argument? ['Although most glass bottles are recyclable if whole, many of the glass bottles removed by activist companies are shattered into pieces.', 'An increasing proportion of the paper, plastics, and metal cans that the groups used to remove is now being recycled.', 'Because litter poses a sanitary health risk to the public, activist groups are doubling their removal efforts in parks and on beaches.', 'People are more likely to save and reuse glass containers than containers made of lighter materials such as paper or plastic.']