大学英语四级阅读[突破英语等级考试].doc

Part II prehension
(35 minutes)
Directions: There are 4 passages in this part. Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A), B), C) and D). You should decide on the best choice and mark the corresponding letter on the Answer Sheet with a single line through the center.
Passage One
Questions 21 to 25 are based on the following passage.
The biggest safety threat facing airlines today may not be a terrorist with a gun, but the man with the puter in business class. In the last 15 years, pilots have reported well over 100 incidents that could have been caused by ic interference. The source of this interference remains unconfirmed, but increasingly, experts are pointing the blame at portable electronic device such as puters, radio and cassette players and mobile telephones.
RTCA, anization which advises the aviation (航空) industry, has mended 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 ic fields might affect an aircraft’puters. Experts know that portable device emit radiation which affects those wavelengths which aircraft use for navigation munication. 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 in