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
(A) describing the limitations of molluscicides that affect feeding behavior (B) proposing alternatives to current methods of controlling slugs and snails (C) emphasizing the need for an alternative to currently available molluscicides (D) explaining how molluscicides are used to control slugs and snails (E) criticizing the use of hazardous material for controlling slugs and snails
The author cites which of the following as a disadvantage of methiocarb?
(A) It contains high levels of aluminum. (B) It may react with acid rain to kill trees. (C) It has been associated with Alzheimer's disease. (D) It may be toxic to some species of fish. (E) It may not be as effective in killing slugs as metaldehyde is.
The passage suggests that methiocarb and metaldehyde would be more effective as slug poisons if it were true that they
(A) disrupt the slug's digestive processes rather than its reproductive functions (B) reduce the slug's ability to taste food (C) begin to affect the feeding behavior of a slug only after it has ingested a lethal dose (D) reach the central pattern generator more quickly (E) accumulate only in the central pattern generator rather than throughout the brain
In the passage, the author is primarily concerned with
(A) describing the limitations of molluscicides that affect feeding behavior (B) proposing alternatives to current methods of controlling slugs and snails (C) emphasizing the need for an alternative to currently available molluscicides (D) explaining how molluscicides are used to control slugs and snails (E) criticizing the use of hazardous material for controlling slugs and snails
因为文章第一段说现有农药的缺点，第二段说替代物含铝物质虽然解决了现有农药的缺点但对环境有危害，所以文章提出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. 也就是说还应该研究一种更好的办法。
我也一直想问这个问题,昨天做的这篇. B和C非常的混，我觉得可能主要看怎么理解这个propose alternatives 了。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。这句只是阐述了need for alternatives.而B 的propose alternatives可能是指的已经提出来了具体的solution ,这点和原文不同
38为什么选C不选A呢？ 原文 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. 说的是在接受lethal dose之前有一系列的影响呀~C说的是在接受Lethal dose 之后才有影响
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发表于 2007-9-22 12:09:00
C) 
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