The biggest safety threat facing airlines today may not be a terrorist with a gun, but the man with the portable computer in bus

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问题     The biggest safety threat facing airlines today may not be a terrorist with a gun, but the man with the portable computer in business class. In the last 15 years, pilots have reported that well over 100 incidents could have been caused by electromagnetic interference. The source of this interference remains unconfirmed, but increasingly, experts are pointing the blame at portable electronic device such as portable computers, radio and cassette players and mobile telephones.
    RTCA, an organization which advises the aviation (航空) industry, has recommended that all airlines ban (禁止) such devices from being used during "critical" stages of flight, particularly take-off and landing. Some experts have gone further, calling for a total ban during all flights. Currently, rules on using these devices are left up to individual airlines. And although some airlines prohibit passengers from using such equipment during take-off and landing, most are reluctant to enforce a total ban, given that many passengers want to work during flights.
    The difficulty is predicting how electromagnetic fields might affect an aircraft’s computers. Experts know that portable device emit radiation which affects those wavelengths which aircraft use for navigation and communicatioa But, because they have not been able to reproduce these effects in a laboratory, they have no way of knowing whether the interference might be dangerous or not.
    The fact that aircraft may be vulnerable (易受损的) to interference raises the risk that terrorists may use radio systems in order to damage navigation equipment. As worrying, though, is the passenger who can’t hear the instructions to turn off his radio because the music’s too loud. (275 words)
The passage is mainly about______.

选项 A、a new regulation for all airlines
B、the defects of electronic devices
C、a possible cause of aircraft crashes
D、effective safety measures for air flight

答案C

解析 本题属于主题归纳题。本文主要讨论随身携带的电子设备产生的电磁干扰,可能导致飞行器安全导航系统故障,从而可能导致飞机失事这一主题。因此选C。
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