The number of codfish in the North Atlantic has declined substantially as the population of harp seals has increased from two million to more than three million. Some blame the seal for the shrinking cod population, but cod plays a negligible role in the seal' s diet. It is ttherefore unlikely that the increase in the seal population has contributed significantly to the decline in the cod population. Which one of the following, if true, most seriously weakens the argument? ['The harp seal thrives in water that is too cold to support a dense population of cod.', "Cod feed almost exclusively on capelin, a fish that is a staple of the harp seal's diet.", 'Water pollution poses a more serious threat to cod than to the harp seal.', 'People who fish for cod commercially are inconvenienced by the presence of large numbers of seals near traditional fishing grounds.']