Medical Investigator: "Podiatrists initially assumed that Meyer' s Rash, an itchy rash between the toes, was a fungal infection similar to athlete' s foot. <b> At first, only Dr. Pannikar argued that Meyer' s Rash was viral in nature. </b> All anti-fungal medications proved utterly ineffective in addressing Meyer' s Rash. Now, recent antibody studies seem to suggest, quite surprisingly, that Meyer' s Rash is caused by a virus. " In the medical investigator's argument, the portion in boldface plays which of the following roles? ['It provides evidence in support of the main conclusion of the argument.', 'It introduces a judgment that the argument opposes.', 'It is the main conclusion of the argument.', 'It presents an explanation that the argument concludes is correct.']