* The reason that man cannot live on sea water is that the human kidney cannot excrete salts in a concentration of more than about 2 percent.

人类不能靠海水生活的原因是人的肾不能排泄浓度超过约2%的盐分。（定语从句译为“的”字结构）

* The cornea is a part of the eye that helps focus light to create an image on the retina.

角膜是眼睛的一部分，它帮助在视网膜上聚光产生物像。（定语从句转译为并列句）

* A body that contains only atoms with the same general properties is called an element.

一切物质，如果它包含的原子性质相同，则称为元素。（定语从句转译为条件状语从句）

3. 引导状语从句

(1) that常用来引导表示目的和结果的状语从句，汉译时可适当增译表示这些概念的词语。如：

* The atmosphere is a mixture of substances that have such low freezing and boiling points that they exist as gases through a wide range of temperatures.

大气是几种物质的混合物，这些物质的凝固点及沸点十分低，以致在很大的温度范围内，它们都以气态存在。（ that引导结果状语从句）

* Modern aircraft are so heavy that the wings must develop a very large lift force in order to sustain the aircraft.

现代飞机如此之重，以致要支撑住飞机，机翼必须产生极大的升力。（that引导结果状语从句）