2014年4月12日中国大陆托福考试全真试题英文还原

　　Reading

　　①

　　Venus, which was named after the goddess of love and beauty, is often recognized as Earth's twin because both worlds share a similar size, surface composition and have an atmosphere with a complex weather system. But along with these mutual features are the differences between the two planets, which have made one prosperous with life and another not.

　　Venus, unlike the earth, orbits near the sun, which causes a significant temperature gap between day and night. Also, the close distance to the sun caused Venus to suffer from the redundant heat from the sun, which makes it impossible for liquid water to exist on Venus; and caused Venus to orbit the sun at a fascinating velocity, in the meanwhile, the water gas started to be thrown into the space because of the tremendous centrifugal force.

　　On Earth today, people are constantly worrying about the greenhouse effect. Venus, if we pay minor attention to its atmosphere, is a planet surrounded with carbon dioxide. The atmosphere of Venus is 90 times denser than that on Earth and is consisted of 96.5% of CO2 and a 3% of Nitrogen, which means that both planets have the same amount of Nitrogen on their atmospheres. Surprisingly the CO2 on Earth is stored on calcite type rocks and if we release the CO2 stuck in these rocks, it would amount to the same amount of CO2 in Venus atmosphere. And it is precisely the high CO2 concentration that raised the temperature over the surface to more than 470'C.

　　Much of the Venusian surface appears to have been shaped by volcanic activity. Venus has several times as many volcanoes as Earth, and it possesses 167 large volcanoes that are over 100 km across. The only volcanic complex of this size on Earth is the Big Island of Hawaii. This is not because Venus is more volcanically active than Earth, but because its crust is older. Earth's oceanic crust is continually recycled by subduction at the boundaries of tectonic plates, and has an average age of about 100 million years, whereas the Venusian surface is estimated to be 300-600 million years old.

　　In contrast to Venus, the Earth is a water globe enjoying with the company of various creatures, mountains and rivers. The ideal environment (abundant liquid water, suitable temperature, enough oxygen, etc.) gave rise to life on earth. And the complex landscapes made it possible for creatures to be diversified.

　　②

　　Irrigation in Mesopotamia

　　The first successful efforts to control the flow of water were in Mesopotamia, where the remains of the prehistoric irrigation works still exist. In ancient Egypt, the construction of canals was a major endeavor of the pharaohs and their servants, beginning in Scorpio's time. One of the first duties of provincial governors was the digging and repair of canals. The land was checker boarded with small basins, defined by a system of dikes. Problems regarding the uncertainty of the flow of the Nile were recognized. During very high flows, the dikes were washed away and villages flooded, drowning thousands. During low flows, the land did not receive water, and no crops could grow. These consisted of a bucket on the end of a cord that hung from the long end of a pivoted boom.

　　The Sumerians in southern Mesopotamia built city walls and temples and dug canals that were the world's first engineering works. It is also of interest that these people, from the beginning of recorded history, fought over water rights. Irrigation was extremely vital to Mesopotamia, Greek for "the land between the rivers." Flooding problems were more serious in Mesopotamia than in Egypt because they carried several times more silt per unit volume of water than the Nile. This resulted in rivers rising faster and changing their courses more often in Mesopotamia。

　　Both the Mesopotamian irrigation system and that in the Egyptian delta were of the basin type, which were opened by digging a gap in the embankment and closed by placing mud back into the gap. Water was hoisted using the swape, as in Egypt. Laws in Mesopotamia not only required farmers to keep their basins and feeder canals in repair but also required everyone to help with hoes and shovels in times of flood or when new canals were to be dug or old ones repaired. Some canals may have been used for 1,000 years before they were abandoned and others were built. Even today, 4,000 to 5,000 years later, the embankments of the abandoned canals are still present. These canal systems, in fact, supported a denser population than lives there today. Over the centuries, the agriculture of Mesopotamia began to decay because of the salt in the alluvial soil.

　　③

　　There are lives on the Pacific islands. The temperature changes make the life on it possible. There is a special kind of birds. They can lay eggs on the floor and build their nest on the floor. This adaption is developed by the changes of the climate and by the changes of the environment. This is not only happen in the pacific islands now, it also happens on the other place such as the Indian ocean. The adaption like this has huge impact to animals.

　　The South Pacific islands were once clothed in tropical moist and dry forests, including rainforests on the higher islands. Forests' relative isolation, large size and complex topography and unusual biogeographic history have all contributed to the archipelagos' highly endemic biota.

　　Pacific islands is notable for having an endemic family of primitive tree, the

　　Degeneraceae, distantly related to magnolias. There are 27 nativeparrots, 4 pigeons, and a rail that are all endemic.

　　Tuamotus is an archipelago comprising 76 islands and coral atolls. The endemic parrot, the Henderson lory, feeds largely on the nectar of 2 plant species, a degree of specialization unknown in nectarivorous birds elsewhere.