[单项选择] Commuter trains are often stuffy and crowded, and they frequently fail to run on time. As if that were not bad enough, physicist Hondon published a paper that gave commuters yet another reason to feel uncomfortable. Dr. Hondon examined mobile-phone usage in enclosed spaces such as railway carriages, buses and lifts, all of which are, in essence, metal boxes. His model predicted that a large number of passengers crowded together, all talking, sending text messages, or browsing the web on their phones, could produce levels of electromagnetic radiation that exceed international safety standards. That is because the radio waves produced by each phone are reflected off the metal walls of the carriage, bus or lift. Enough radiation escapes to allow the phone to communicate with the network, but the rest fills the inside of the carriage with bouncing microwaves. This sounds worrying. However, in a paper published recently, Jaime Ferrer and Lucas Fernández-Seivane from the Univer
A. Because he sets up a model of international radiation safety standards.
B. Because he put forward that the radiation produced by all the mobile phones in the enclosed spaces will bounce around and be harmful.
C. Because the commuters worried that the metal walls of the railway carriage will threaten their health.
D. Because the commuters are afraid that the use of mobile phone will be banned in the railway carriage.