It is a conclusion that is claimed to follow from the premise that microorganisms are too numerous for medicines to eliminate entirely. It is a generalization used to predict the response of microorganisms to the medicines humans use to kill them. It is a premise offered in support of the claim that most disease-causing microorganisms are able to evolve immunities to medicines while retaining their ability to infect humans. It is a conclusion for which a description of the responses of microorganisms to the medicines designed to cure the diseases they cause is offered as support.
It is unlikely that the world will ever be free of disease. Most diseases are caused by very prolific microorganisms whose response to the pressures medicines exert on them is predictable: they quickly evolve immunities to those medicines while maintaining their power to infect and even kill humans.
Which one of the following most accurately describes the role played in the argument by the claim that it is unlikely that the world will ever be free of disease?