Most farmers attempting to control slugs and snails turn to baited slug poison, or molluscicide, which usually consists of a bran pellet containing either methiocarb or metaldehyde. Both chemicals are neurotoxins that disrupt that part of the brain charged with making the mouth move in a coordinated fashion—the "central pattern generator"—as the slug feeds. Thus, both neurotoxins, while somewhat effective, interfere with the slugs' feeding behavior and limit their ingestion of the poison, increasing the probability that some will stop feeding before receiving a lethal dose. Moreover, slugs are not the only consumers of these poisons: methiocarb may be toxic to a variety of species, including varieties of worms, carabid beetles, and fish.

Researchers are experimenting with an alternative compound based on aluminum, which may solve these problems, but this may well have a limited future as we learn more about the hazards of aluminum in the environment. For example, some researchers suggest that acid rain kills trees by mobilizing aluminum in the soil, while others have noted that the human disease Alzheimer's is more prevalent in areas where levels of aluminum in the soil are high. With farmers losing as much as 20 percent of their crops to slugs and snails even after treatment with currently available molluscicides, there is considerable incentive for researchers to come up with better and environmentally safer solutions.


The author suggests that which of following is true of the "alternative compound" mentioned in the highlighted text?


It is more effective in destroying snails than in destroying slugs.

It begins to affect slugs' feeding behavior before they ingest a lethal dose.

It affects more species of fish than does metaldehyde

It may not be environmentally safer than methiocarb

It may be less damaging to trees than metaldehyde

考题讲解

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答案是 D。作者在高亮的文本中暗示着这个替代化合物可能不如 methiocarb 环保。他指出,随着我们对环境中铝的危害越来越多的了解,这种替代化合物可能具有有限的未来。他还说,一些研究人员认为酸雨通过机动土壤中的铝来杀死树木,而另一些研究人员则注意到,土壤中铝水平较高的地区较容易发生老年痴呆症。因此,D 选项正确,因为它暗示着所提及的替代物可能不如 methiocarb 环保。

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Prep2008E1-RC