题目内容：
根据材料，回答题。 Singing Alarms Could Save the Blind
If you cannot see, you may not be able to find your way out of a burning building--and that could be fatal. A company in Leeds could change all that_________ (51 ) directional sound alarms capable of guiding you to the exit.
Sound Alert, a company " _________ (52) the University of Leeds, is installing the alarms in a residential home for_________ ( 53 ) people in Sommerset and a resource centre, for the blind in Cumbria. _________ (52 ) produce a wide range of frequencies that enable the brain to determine where the_________ ( 55 ) is coming from.
Deborah Withington of Sound Alert says that the alarms use most of the frequencies that can be _________ (56) by humans. "It is a burst Of white noise _________ (57) people say sounds hkestatic on the radio," she says. "Its life-saving potential is great. "
She conducted an experiment in which people were filmed by thermal-imaging cameras trying to find their way out of a large_________ (58) room. It _________ (59) them nearly four minutes to find the door_________ (60) a sound alarm, but only 15 seconds with one.
Withington studies how the brain _________ (61) sounds at the university. She says that the_________ (62) of a wide band of frequencies can be pinpointed mote easily than the source of a
narrow band. Alarms_________ (63)the same concept have already been installed on emergency vehicles.
The alarms will also include rising or failing frequencies to indicate whether people should goup_________ (64) down stairs. They were _________ ( 65 ) with the aid of a large grant from British
Nuclear Fuels.
回答(51)题 A．without
B．with
C．having
D．selling
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