The problem that environmental economics aims to remedy is the following: people making economic decisions cannot readily compare environmental factors, such as clean air and the survival of endangered species, with other costs and benefits. As environmental economists recognize, solving this problem requires assigning monetary values to environmental factors. But monetary values result from people comparing costs and benefits in order to arrive at economic decisions. Thus, environmental economics is stymied by what motivates it. If the considerations advanced in its support are true, the passage's conclusion is supported ['at best weakly, because the passage fails to establish that economic decision-makers do not by and large take adequate account of environmental factors', 'not at all, since the argument is circular, taking that conclusion as one of its premises', 'strongly, on the assumption that monetary values for environmental factors cannot be assigned unless people make economic decisions about these factors', 'strongly, unless economic decision-making has not yet had any effect on the things categorized as environmental factors']