1999年6月大学英语四级考试试题及答案 |
2006-2-17 1:12:19 点击数： 进入论坛 |
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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 well over 100 incidents that could have been caused by electromagnetic interference. The source of this interference remains unconfirmed, but increasingly, experts are pointing the blame at portable electronic devices 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 light, particularly takeoff 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 takeoff 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 devices emit radiation which affects those wavelengths which aircraft use for navigation and communication. 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 system in order to damage navigation equipment. As worry-
ing, though, is the passenger who can't hear the instructions to turn off his radio because the music's too loud.
21.The passage is mainly about_______.
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
22.What is said about the over 100 aircraft incidents in the past 15 years?
A) They may have been caused by the damage to the radio systems.
B) They may have taken place during takeoff and landing.
C) They were proved to have been caused by the passengers' portable computers.
D) They were suspected to have resulted from electromagnetic interference.
23.Few airlines want to impose a total ban on their passengers using electronic devices
because_______.
A) they don't believe there is such a danger as radio interference
B) the harmful effect of electromagnetic interference is yet to be proved
C) most passengers refuse to take a plane which bans the use of radio and cassette |
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| 2007年4月大考时间 |
| 2007年4月21日-4月22日 |
| 2007年7月加考时间 |
| 2007年7月7日-7月8日 |
| 2007年10月大考时间 |
| 2007年10月27日-10月28日 |
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