| 71. | The lake was not a natural one, but a man-made reservoir. |
| 村庄已不复存在，因为已经为水所淹，山谷也被水淹没了。
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| 72. | This rabbit had no natural enemies in the Antipodes, so that it multiplied with that promiscuous abandon characteristic of rabbits. |
| 这种兔子在澳大利亚及新西兰没有天敌，因此便以兔子所特有的杂乱交配迅猛繁殖起来。
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| 73. | Porpoises and sharks are natural enemies. |
| 海豚和鲨鱼是天然仇敌，
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| 74. | These ocean waves are among the earth's most complicated natural phenomena. |
| 这些海浪属于地球上最复杂的自然现象。
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| 75. | The undulating waves of the open sea are generated by three natural causes: wind, earth movements or tremors, and the gravitational pull of the moon and the sun. |
| 公海上起伏的波浪是由3个自然因素构成的：风、地球的运动或震颤和月亮、太阳的引力。
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| 76. | Although perhaps only 1 per cent of the life that has started somewhere will develop into highly complex and intelligent patterns, so vast is the number of planets, that intelligent life is bound to be a natural part of the universe. |
| 虽然在已经产生生命的某个地方，可能只有1%会发展成高度复杂有智力的生命形态，但是行星的数目是那么庞大，有智力的生命必然是宇宙的自然组成道听部分。
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| 77. | It is the natural frequency of emission of the hydrogen atoms in space and was discovered by us in 1951; |
| 这个频率是空间氢原子释放的自然频率，是在1951年被人类发现的。
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| 78. | Their life is a natural harmony. |
| 他们的生活是一种自然的和谐，
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| 79. | Morocco and California are bits of the Earth in very similar latitudes, both on the west coasts of continents with similar climates, and probably with rather similar natural resources. |
| 摩洛哥和加利福尼亚是地球上纬度极其相似的两个地方，都在各自大陆的西海岸，气候相似，自然资源也可能相似。
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| 80. | If he could pass off the death as occurring from natural causes, the true cause might not attract attention. |
| 如果他能使病人的死亡显得是正常死亡、人们也许不会注意到真正的死因。
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