Some species are called "indicator species"because the loss of a population of such a species serves as an early warning of problems arising from pollution. Environmentalists tracking the effects of pollution have increasingly paid heed to indicator species; yet environmentalists would be misguided if they attributed the loss of a population to pollution in all cases. Though declines in population often do signal environmental degradation, they are just as often a result of the natural evolution of an ecosystem. We must remember that, in nature, change is the status quo. Which one of the following most accurately expresses the argument's conclusion? ['The loss of a specific population is often the result of natural changes in an ecosystem and in such cases should not be resisted.', "Environmentalists' use of indicator species in tracking the effects of pollution is often problematic.", 'The loss of a specific population should not always be interpreted as a sign of environmental degradation.', "The loss of a specific population as a result of pollution is simply part of nature's status quo."]