Passage 1:
　　It is common knowledge that forecasting is an attempt by meteorologists to determine what weather will be like in the future. Hindcasting is the opposite of forecasting, an attempt to determine what weather was like in the past. Meteorologists wish that records of weather had been kept in full for at least a few millennia, but it has been only in the last century that detailed records of the weather have been kept. Thus, meteorologists need to hindcast the weather, and they do so by using all sorts of information from other fields as diverse as archeology, botany, geology, literature, and art. These pieces of information from other fields that are used as a basis for drawing conclusions about what the weather must have been like at some point in the past are called proxies.
　　Passage 2:
　　The Sahara is a massive desert, the world’s largest, in fact. It is approximately equal in size to the United States and covers more than 9 million square kilometers. It is more than 5,500 kilometers from east to west and 2,000 kilometers from north to south.
　　The Sahara has a very dry climate. The average annual rainfall is not even 10 centimeters, and may areas receive less that 2 centimeters per year. In the very driest places, it rains only about once a century.
　　There is little surface water in the Sahara. The Nile River does run through the Sahara, and there are some oases there, but otherwise the surface is dry. Of the oases in the Sahara, about 90 are large enough to support tiny villages.
　　Passage 3:
　　It is very common in English for one word to have many different meanings. This condition, where one word has different meanings, is known as polysemy. (This term comes from poly- meaning “many” and sem- meaning “meaning”.)
　　Sound is one such polysemic word. As a noun, it refers to a noise (as in a loud sound) or a body of water (as in Puget Sound). As an adjective, it can refer to a state of health (as in sound mind and body). It can also be an intransitive verb (as in sound angry), a transitive verb (as in sound the alarm), or part of a verb phrase as an outburst (as in sound off) and an inquiry (as in sound out).
　　You may think that the word sound is a truly wondrous polysemic word. After all, its definitions cover seven pages in one major dictionary and include 19 meanings as a noun, 12 meanings as an adjective, 12 meanings as a verb (some transitive and some intransitive ), 4 meanings in verb phrases, and 2 meanings as an adverb.
　　But what about the extraordinary word set? It looks like such a short, simple word, only three little letters in all. However, if you look it up in an unabridged dictionary, you will find at least 57 meanings for set when it is used as a noun and over 120 meanings when it is used as a verb.
　　Passage 4：
　　1.Paper is different from other waste produce because it comes from a sustainable resource: trees. Unlike the minerals and oil used to make plastics and metals, trees are replaceable. Paper is also biodegradable, so it does not pose as much threat to the environment when it is discarded. While 45 out of every 100 tonnes of wood fibre used to make paper in Australia comes from waste paper, the rest comes directly from virgin fibre from forests and plantations. By world standards, this is a good performance since the world-wide average is 33% waste paper. Governments have encouraged waste paper collection and sorting schemes and at the same time, the paper industry has responded by developing new recycling technologies that have paved the way for even greater utilization of used fibre. As a result, industry’s use of recycled fibres is expected to increase at twice the rate of virgin fibre over the coming years.
　　2.Already, waste paper constitutes 70% of paper used for packaging and advances in the technology required to remove ink from the paper have allowed a higher recycled content in newsprint and writing paper. To achieve the benefits of recycling, the community must also contribute. We need to accept a change in the quality of paper products; for example stationery may be less white and of a rougher texture. There also needs to be support from the community for waste paper collection programs. Not only do we need to make the paper available to collectors but it also needs to be separated into different types and sorted from contaminants such as staples, paperclips, string and other miscellaneous items.
　　3.There are technical limitations to the amount of paper which can be recycled and some paper products cannot be collected for re-use. These include paper in the form of books and permanent records, photographic paper and paper which is badly contaminated. The four most common sources of paper for recycling are factories and retail stores which gather large amounts of packaging material in which goods are delivered, also offices which have unwanted business documents and computer output, paper converters and printers and lastly households which discard newspapers and packaging material. The paper manufacturer pays a price for the paper and may also incur the collection cost.
　　4.Once collected, the paper has to be sorted by hand by people trained to recognize various types of paper. This is necessary because some types of paper can only be made from particular kinds of recycled fibre. The sorted paper then has to be repulped or mixed with water and broken down into its individual fibres. This mixture is called stock and may contain a wide variety of contaminating materials, particularly if it is made from mixed waste paper which has had little sorting. Various machinery is used to remove other materials from the stock. After passing through the repulping process, the fibres from printed waste paper are grey in color because the printing ink has soaked into the individual fibres. This recycled material can only be used in products where the grey color does not matter, such as cardboard boxes, but if the grey color is not acceptable, the fibres must be d-inked. This involves adding chemicals such as caustic soda or other alkalis, soaps and detergents, water-hardening agents such as calcium chloride, frothing agents and bleaching agents. Before the recycled fibres can be made into paper, they must be refined or treated in such a way that they bond together.
　　5.Most paper products must contain some virgin fibre as well as recycled fibres and unlike glass, paper cannot be recycled indefinitely. Most paper is down-cycled which means that a product made from recycled paper is of an inferior quality to the original paper. Recycling paper is beneficial in that it saves some of the energy, labor and capital that goes into producing virgin pulp. However, recycling requires the use of fossil fuel, a non-renewable energy source, to collect the waste paper from the community and to process it to produce new paper. And the recycling process still creates emissions which require treatment before they can be disposed of safely. Nevertheless, paper recycling is an important economical and environmental practice but one which must be carried out in a rational and viable manner for it to be useful to both industry and the community.
　　Some questions:
　　1: What can be the best title of this article?
　　--Paper recycling
　　2: What’s the main idea of the 1st paragraph?
　　--the background and significance of paper recycling.
　　3: What’s the main idea of the 2nd paragraph?
　　--Advances in technology and the role the community can play in promoting paper recycling.
　　4: What’s the main idea of the 3rd paragraph?
　　--limitations in paper recycling and the four major sources of waste paper
　　5: What’s the main idea of the 4th paragraph?
　　--troubles with paper recycling process
　　6: What’s the main idea of the 5th paragraph?
　　--the troubles and significance of paper recycling