科技

A compass is usually considered mandatory but you have to be careful using it.

指南针通常被认为是强制性的，但你要小心使用。

As a result of bronchial tube distortion,narrow,causes a row of phlegm impeded to cause the trachea and the lungs repeatedly infects,creates the tube cavity to be narrow,the gas channel resistance advances,causes the oxygen deficit and the carbon dioxide remains.

由于支气管的扭曲，狭窄，导致排痰不畅使气管及肺部反复感染，造成管腔狭窄，气道阻力增高，引起缺氧及二氧化碳潴留。