[单项选择]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 industry, has recommended that all airlines ban 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 pas
A. Because it is extremely dangerous to conduct such research on an airplane.
B. Because experts lack adequate equipment to do such research.
C. Because research scientists have not been able to produce the same effects in labs.
D. Because it remains a mystery what wavelengths are liable to be interfered with.