题目选项分析

The recycling of municipal solid waste is widely seen as an environmentally preferable alternative to the prevailing practices of incineration and of dumping in landfills. Recycling is profitable, as the recycling programs already in operation demonstrate. A state legislator proposes that communities should therefore be required to adopt recycling and to reach the target of recycling 50 percent of all solid waste within 5 years.

Which of the following, if true, most seriously calls into question the advisability of implementing the proposal?

【选项】Existing recycling programs have been voluntary, with citizen participation ranging from 30 percent in some communities to 80 percent in others.