1. 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。

2. 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。

3. Their life is a natural harmony.
    他们的生活是一种自然的和谐，

4. The lake was not a natural one, but a man-made reservoir.
    这不是一个天然湖泊，是一座人工修建的水库。

5. The smoke of one small fire causes no harm to the environment. Natural cleaning processes can clean the particles of smoke from the air.
    小火带来的烟不会危害环境，因为自然净化作用会将空气中的烟尘清除。

6. There is a natural tendency for any relationship based on voluntary affection to come apart, but marriage provides the glue needed to keep a couple together by providing ties of family, in conjunction with the obligations of parents to children.
    任何建立在自发爱恋基础上的关系都会趋于自然终止，但婚姻建立起家庭纽带，以及父母与子女间的责任义务，这就提供了将夫妇联结在一起的粘合剂。

7. Natural disasters like storms and floods have washed away many crops.
    暴风雨和洪水这类自然灾害毁掉了许多庄稼。

8. Natural gas, an outstanding energy fuel, can be used to heat homes, make electricity, and power cars.
    天然气这种优良的能量燃料可以用于家庭取暖、发电和驱动汽车。

9. His desire of returning to his family is natural.
    他想回家是很自然的。

10. However, people cause problems for this natural recycling system.
    但是，人类却给这种大自然的水循环系统制造了许多麻烦。