1. Porpoises and sharks are natural enemies.
    海豚和鲨鱼是天然仇敌，

2. Many natural materials are becoming scarce.
    许多天然原料越来越少.

3. So vast is the number of planets, that intelligent life is bound to be a natural part of the universe.
    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部分。

4. Both on the west coasts of continents with similar climates, and probably with rather similar natural resources.
    都在各自大陆的西海岸，气候相似，自然资源也可能相似。

5. Cleaning this smoke has exceeded the protective ability of natural processes.
    要清除这些烟尘已超出了自然作用的保护能力。

6. Certainly industry has played a significant role in destroying natural areas, generating pollution and using up resources.
    在破坏自然环境、制造污染和消耗能源方面，工业固然起了主要作用，但是我们才是授意者：

7. It is the natural frequency of emission of the hydrogen atoms in space .
    这是空间氢原子“释放”的自然频率.

8. 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。

9. It would not have been very important if he had merely found plasmodium parasites in the tiny stomach, but the parasites were multiplying — suggesting that the mosquito´s stomach was one of their natural homes.
    如果在蚊子微小的腹内他只是发现了疟原虫寄生虫，这个发现还不是个很重要的发现，但是寄生虫在繁殖——这就意味着蚊子的腹内是它们的一个自然之家。

10. It might sink slowly through the soil into the natural holding areas in the rock.
    它也许会通过土地慢慢地渗透到岩层里的天然蓄水区；