In 1967, in response to widespread public concern aroused by medical reports of asbestos related death, the National Medical Res

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问题     In 1967, in response to widespread public concern aroused by medical reports of asbestos related death, the National Medical Research Council (NMRC) organized a committee of enquiry to investigate the health threats associated with the use of asbestos in the building industry. After examining evidences provided by medical researchers and building workers and management, the Council published a report which included advices for dealing with asbestos. The report confirmed the findings of similar research in the United States and Canada. Exposure to relatively small quantities of asbestos fibers, they concluded, was directly responsible for the development of cancers, asbestosis (石棉沉着病) and related diseases. Taking into account evidence provided by economists and building industry management, however, the report assumed that despite the availability of other materials, asbestos would continue to play a major role in the British building industry for many years to come because of its availability and low cost.
    As a result, the Council gave a series of recommendations which were intended to reduce the risks to those who might be exposed to asbestos in working environments. They suggested that, where possible, asbestos-free materials should be employed. In cases where asbestos was employed, it was recommended that it should be used in such a way that loose fibers were less likely to enter the air. The report advised that special care should be taken during work in environments which contain asbestos. Workers should wear protective equipment and take special care to remove dust from the environment and clothing with the use of vacuum cleaner.
    The report identified five factors which determine the level of risk involved. The state and type of asbestos is critical to determining the risk factors. In addition, dust formation was found to be limited where asbestos was used when wet rather than dry.
    The choice of tools was also found to affect the quantities of asbestos particles that enter the air. Machine tools produce greater quantities of dust than hand tools and, where possible, the use of the latter was preferred.
    A critical factor which takes place in risk reduction is the adequate ventilation of the working environment. When work takes place in an enclosed space, more asbestos particles circulate and so natural or machine ventilation should be used. By closely following these advices, it was claimed that exposure can be reduced to a reasonably practical minimum.
According to the passage, exposure to asbestos fibers can cause cancer

选项 A、only when asbestos is used in building industry.
B、only when it is used in large quantities.
C、even if it is used in small quantities.
D、if they are used when wet rather than dry.

答案C

解析 根据题干中的exposure to asbestos fibers定位到第1段倒数第2句。由该句可知,报告认为,接触极少量的石棉纤维就足以引发癌症、石棉沉着病等。由此可见,本题选C。A、B均无原文依据且都使用了绝对化的限定词only,过于绝对的选项通常不是答案,故可排除。D是减少灰尘形成的方法,不符题意,也排除。
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