4. An infra-red system could be useable in both anti-air and anti-ship engagements, but its inherent disadvantages related to some dependence on optical visibility and to sensibilty to interference from natural or man-made sources make it less attractive in the surface than in the air role.

红外系统既可用于对空作战，也可用于对舰作战，但是它有两个固有的缺点：一是对光学能见度有一定的依赖性，二是易受天然或人工干扰源的干扰。因此，该系统的对空作用较之对舰作用更为诱人。

5. From what is stated above, it is learned that the sun's heat can pass through the empty space between the sun and the atmosphere that surrounds the earth, and that most of the heat is dispersed through the atmosphere and lost，which is really what happens in the practical case, but to what extent it is lost has not been found out.

由上述可知，太阳的热量可以穿过太阳与地球大气层之间的真空，而大多热量在通过大气层时都扩散和消耗了。实际发生的情况正是如此。但是热量的损失究竟 达到什么程度，目前尚未弄清。

从以上几个译例中可以看出，在把英语长句拆译成几个短句后，为了使前后衔接紧密，语意贯通，常需增加一些词。

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