The inhalation (吸入) of asbestos particles is associated with a number of lung diseases, such as asbestosis and ___50___ cancer. 
Asbestosis is caused by the entry of asbestos particles into the wall of the alveoli, causing scarring which limits the functioning of the lungs.  The lung ___51___ its elasticity and may change shape.  The initial symptoms of asbestosis are a tightness in the chest and breathlessness.  In its ___52___ stages, sufferers develop the barrel-shaped chests associated with emphysema, cyanosis, (where the skin takes a bluish ___53___ ) and club fingers.
Lung cancer, the generic ___54___ for malignant tumors（肿瘤）of the alveoli and bronchial tubes, has been shown to be directly ___55___ to the inhalation of asbestos particles.  As in the case of asbestosis, there is generally a period of inactiveness which may ___56___ from 25 to 30 years after initial exposure, despite the ___57___of further exposure.  Research suggests that there is a direct correlation between the degree of exposure to asbestos ___58___the incidence of lung cancer.  Where exposure occurs, the level of risk is further ___59___ by cigarette smoking.  Asbestos workers who smoke cigarettes have a 90% greater risk of catching lung cancer than workers who do not ___60___. 
Exposure to blue asbestos has been shown to producemesothelioma, a rare cancer of the outer lining of the lung or pleura.  In a normal population the incidence of mesothelioma is extremely ___61___. Where epidemiological surveys have revealed a higher incidence of the disease, it is almost always related to ___62___ exposure.
___63___ changes in lung tissue caused by exposure to asbestos are pleural plaques and effusions.  The former refer to a thickening of the lining of the chest wall, ___64___ the latter consists of a collection of fluid in the chest region outside the lungs.  Pleural plaques commonly remain undiagnosed and generally have no detrimental effect on health.

A．skin B．blood C．liver D．lung

A．loses B．gains C．improves D．tightens

A．early B．formal C．later D．final

A．size B．color C．sound D．smell

A．noun B．term C．way D．approach

A．related B．revealed C．compared D．exposed

A．disappear B．spread C．live D．extend

A．presence B．activeness C．absence D．intensity

A．and B．alongside C．as well as D．plus

A．decreased B．lost C．doubled D．increased

A．diet B．drink C．smoke D．fare

A．high B．low C．common D．frequent

A．lead B．asbestos C．carbon D．hydrogen

A．Three B．Some C．No D．Other

A．in case B．now that C．whereas D．unless