RC PREP08 Most farmers attempting to control slugs and snail

[ReoW527]

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.

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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
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The OA is C, but I chose E.
I understand fully of this passage, it mainly tells us about three issues:

1. the disadvantages of traditional molluscicide. (para. 1)
2. the disadvantages of alternative molluscicide made of aluminium (para. 2)
3. the future expectation of new molluscicide

However, the point 3, which is merely a sentence, only consists 1/5 of the passage, while the other two points consist 4/5 of the passage.
I searched the forum, but did not find any relevant question, so I post the question to ask the teachers here.
:)

[Sage Pearce-Higgins]

Good analysis of the passage, but choosing an answer based on what fraction of the passage it covers is too simple an approach for a tricky problem such as this one. Let me give you an example:

"It looks like we'll have bad weather: the sky is overcast, a wind has built up, and it's got much colder this afternoon. Moreover, the weather forecast says that there might even be snow. Having a barbecue tomorrow is not a good plan."

Now, what is the author 'primarily concerned' with in the passage - the weather or the barbecue? Clearly the information about the weather is simply a stepping stone to the warning about the barbecue. Never mind that the barbecue only get's a short mention at the end: it's actually the main point, the conclusion of the argument.

The same goes for the passage above. The final sentence is actually the main point. To make this clearer, let me give my analysis of the 3 sections of the passage that you've identified:
1. the disadvantages of traditional molluscicide
2. a discussion of an alternative molluscicide made of aluminium [note that it includes some positive description and is not only critical]
3. a conclusion: statement of a problem with apparently no solution