【托福培训-阅读】托福阅读主旨题如何判断主旨与细节

托福阅读最后一道大题是六选三，即从六个选项中选取三个，加上给出的句子，合成对全文的概括。正确选项的特征是"the most important ideas in the passage"，是文章的核心信息；错误选项的典型特征是文章细节。下面以两个题目分别来看如何判断主旨信息和细节信息。

　　文章题目：MINERALS AND PLANTS

　　下面分别是没段段首的信息：

　　Paragraph 1 Research has shown that certain minerals are required by plants for normal growth and development.

　　Paragraph 2 Mineral deficiencies can often be detected by specific symptoms such as chlorosis (loss of chlorophyll resulting in yellow or white leaf issue), necrosis (isolated dead patches), anthocyanin formation (development of deep red pigmentation of leaves or stem), stunted growth, and development of woody tissue in an herbaceous plant.

　　Paragraph 3 Much of the research on nutrient deficiencies is based on growing plants hydroponically, that is, in soilless liquid nutrient solutions.

　　Paragraph 4 While mineral deficiencies can limit the growth of plants, an overabundance of certain minerals can be toxic and can also limit growth.

　　Paragraph 5 Scientists have known for some time that certain plants, called hyper accumulators, can concentrate minerals at levels a hundredfold or greater than normal.

　　Paragraph 6 Only recently have investigators considered using these plants to clean up soil and waste sites that have been contaminated by toxic levels of heavy metals - an environmentally friendly approach known as phytoremediation.

　　题目：

　　Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some answer choices do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.

　　Plants need to absorb certain minerals from the soil in adequate quantities for normal growth and development.

　　1. Some plants are able to accumulate extremely high levels of certain minerals and thus can be used to clean up soils contaminated with toxic levels of these minerals.

　　2. Though beneficial with lower levels, high levels of salts, other minerals, and heavy metals can be harmful to plants.

　　3. When plants do not absorb sufficient amounts of essential minerals, characteristic abnormalities result.

　　4. Because high concentrations of sodium chloride and other salts limit growth in most plants, much research has been done in an effort to develop salt-tolerant agricultural crops.

　　5. Some plants can tolerate comparatively low levels of certain minerals, but such plants are of little use for recycling nutrients back into depleted soils.

　　6. Mineral deficiencies in many plants can be cured by misting their roots with a nutrient solution or by transferring the plants to a soilless nutrient solution.

　　正确选项是123。不难发现，选项1对应第5和6段；选项2对应第4段；选项3对应第2段。这是因为，所谓的文章主要信息，其实就是某一段或几段的主旨信息。因此，如果有的选项不确定，可以回到文中把每段的主旨信息找到，作为判断的依据。

　　除了选出正确选项外，还要擅长排除错误选项。常见的错误选项是文章提到的细节信息。那么细节信息的特征是什么？先看例子。

　　文章题目：APPLIED ARTS AND FINE ARTS

　　题目：

　　An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.

　　This passage discusses fundamental differences between applied-art objects and fine-art objects.

　　Answer Choices

　　○Applied-art objects fulfill functions, such as containing or sheltering, and objects with the same function have similar characteristics because they are constrained by their purpose.

　　○It is easy to recognize that Shang Dynasty vases are different from Inca vases.

　　○Fine-art objects are not functional, so they are limited only by the properties of the materials used.

　　○Renaissance sculptors learned to use iron braces to strengthen the internal structures of bronze statues.

　　○In the twentieth century, fine artists and applied artists became more similar to one another in their attitudes toward their materials.

　　○In all periods, fine artists tend to challenge the physical limitations of their materials while applied artists tend to cooperate with the physical properties of their materials.

　　错误选项为245.它们共同的特点是：细节信息，具体体现在：选项2里的Shang Dynasty vases, 选项4的Renaissance sculptors, 选项5里的in the twentieth century和similar。这些细节信息的具体特征是：人名、地名、数字、年代等等。尤其当这些信息出现在句子主干处时，要格外当心！