Microbiologist: A lethal strain of salmonella recently showed up in a European country, causing an outbreak of illness that killed two people and infected twenty-seven others. Investigators blame the severity of the outbreak on the overuse of antibiotics, since the salmonella bacteria tested were shown to be drug-resistant. But this is unlikely because patients in the country where the outbreak occurred cannot obtain antibiotics to treat illness without a prescription, and the country's doctors prescribe antibiotics less readily than do doctors in any other European country. Which of the following, if true, would most weaken the microbiologist's reasoning? ['Salmonella has been shown to spread easily along the distribution chains of certain vegetables, such as raw tomatoes.', 'Use of antibiotics in two countries that neighbor the country where the outbreak occurred has risen over the past decade.', 'Physicians in the country where the outbreak occurred have become hesitant to prescribe antibiotics since they are frequently in short supply.', 'People in the country where the outbreak occurred often consume foods produced from animals that eat antibiotics-laden livestock feed.']