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.


In the passage, the author is primarily concerned with


describing the limitations of molluscicides that affect feeding behavior

proposing alternatives to current methods of controlling slugs and snails

emphasizing the need for an alternative to currently available molluscicides

explaining how molluscicides are used to control slugs and snails

criticizing the use of hazardous material for controlling slugs and snails

考题讲解

题目分析:

题目释义:

主旨题目

考点:

主旨(Main idea)   
旨在考察我们对文章整体的把握程度,对文章的结构的分析能力和把控能力,以及对作者逻辑的判断。

这道题目可能有些难选,因为作者通篇看似讲了两个消灭鼻涕虫的方法,其实一个是现有的方法,因为这个方法不好,迫切需要改进,所以又有人提出的另一个新的方法,可是新方法的缺陷也十分严重,结尾作者这样的情况刺激研究员找出新方法。但是这道题想要直奔答案选项不很容易,用排除法可以顺利解题。



选项分析:

A选项:描述影响饮食能力的软体动物驱除药的限制条件。这个内容属于第一段描述的内容,不是全文的主旨,是细节。

B选项:提出控制鼻涕虫和蜗牛的另一种方法。这个选项容易误选。作者确实提出了令一个方法,但是作者反驳了这个方法并在结尾说需要其他的方法,说明作者不是为了提出第二个方法才写的文章。

C选项:Correct. 强调现在的软体动物驱除药需要改变。其实作者一开篇就强调说现在的方法不好,进而说新的方法也不好,需要别的方法。所以作者的目的是要强调需要另外的方法。

D选项:
解释软体动物驱除药是如何控制鼻涕虫和蜗牛的。这也属于第一段的内容,不是全文的主旨。

E选项:
批评用有危险的材料来控制鼻涕虫和蜗牛。作者提出了两个方法都有危险,但是没有批评这两个方法的意思,只是单纯的陈述说这两个方法不行。

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Prep2007E2-RC