北京新航道为大家提供托福培训，解决托福各方面的难题。我们都知道，托福阅读题量大，时间紧迫，所以说事先掌握的背景知识有利于自己做题的速度和效率。遇到难句难文也有理据去猜测一下。下面就由北京新航道的小编为大家奉上精心整理的一些有助于阅读的背景知识。

　　the code of Hammurabi

　　Hammurabi was the ruler who chiefly established the greatness of Babylon, the world's first metropolis. Many relics of Hammurabi's reign ([1795-1750 BC]) have been preserved, and today we can study this remarkable King....as a wise law-giver in his celebrated code. . .

　　by far the most remarkable of the Hammurabi records is his code of laws, the earliest-known example of a ruler proclaiming publicly to his people an entire body of laws, arranged in orderly groups, so that all men might read and know what was required of them. The code was carved upon a black stone monument, eight feet high, and clearly intended to be reared in public view. This noted stone was found in the year 1901, not in Babylon, but in a city of the Persian mountains, to which some later conqueror must have carried it in triumph. It begins and ends with addresses to the gods. Even a law code was in those days regarded as a subject for prayer, though the prayers here are chiefly cursings of whoever shall neglect or destroy the law.

　　Yet even with this earliest set of laws, as with most things Babylonian, we find ourselves dealing with the end of things rather than the beginnings. Hammurabi's code was not really the earliest. The preceding sets of laws have disappeared, but we have found several traces of them, and Hammurabi's own code clearly implies their existence. He is but reorganizing a legal system long established.

　　Plant adaptation to the desert(背景材料)

　　Cactus adaptations.

　　The secret to the superior endurance of cacti lies in their adaptations. Over millions of years, through natural selection, only the strongest and best adapted species survived.

　　As you know, it is very dry in the desert. Plants that adapt to this are known as xerophytes (from xeros, dry and phyton, plant). There are plants that avoid the dry season by sprouting from seed just after the spring rain and growing very fast so that by the time the dry season comes, they have already produced a lot of seeds and died. These seeds lie on the soil for the dry season and sprout again in spring and the cycle repeats. Other xerophytes simply drop their leaves and stay dormant for the winter. But there is another special type of xerophyte which stores water in its fleshy tissues. Such plants are called succulents (from succus, juicy). The cactus is a typical example of a succulent.来源：北京新航道托福培训

　　If you cut a cactus open, you see a juicy, slimy tissue. This is where the moisture is stored for the dry season. The part between the middle circle (or pith) and just under the very green part of the plant (or palisade parenchyma) just under the skin is allocated for the storage of water and food for the plant. This is a type of spongy parenchyma and can take up up to 85% of the plant's volume. This is a major adaptation in the desert. Because the plant remains completely alive during the dry season and there is no need for it to dry up and lose everything, makes it possible for the plant to grow to large sizes. Another advantage is that the plant retains supplies (in the form of starch) for the winter so that it can flower right away in spring without accumulating more supplies (as most plants need to do in spring). The whole purpose of storing supplies for the winter is mostly to energize flowering in spring but it also lets the cactus start growing much sooner.

　　Flowering plants breathe and transpire (evaporate water from their surface) through closeable microscopic pores called stomates on the leaves or stems. To do this, their pores have to be open. In most plants these are open all day and on warm nights. But for cacti this is inconvenient as in daytime it is very hot and thus the plant would lose a lot of water through evaporation. So the cactus must close them in the daytime. But then it cannot breathe or photosynthesize (the process where sugars are made from carbon dioxide and water and releasing oxygen using the sun's energy). Succulents have an adaptation to that. Their stomates are closed during the day and are open at night, when it is not that hot and store carbon dioxide in its tissues as crassulean acid and then turn it back to carbon dioxide in the daytime. This process is called crassulean acid metabolism or CAM and it is a very smart way of respiring in the desert.

　　If we look at the outside of the plant, we notice that there is a tough leathery skin covering the plant, we can also notice the presence of ribs and spines and sometimes fur. These are all very smart adaptations. They serve mainly for surviving heat but are also used as defense.

　　上面是一些实用的阅读背景知识，希望大家能够看一看，理解一下。在真正的考试过程中极有可能会用到。了解的北京对于做好阅读有很大的帮助。希望各位同学都能够取得理想的成绩。

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