单项选择题

Questions 11-15 are based on the following passager:  Firefighter are often asked to speak to school and community groups the importance of fire safety,partcularly fire prevention and detection,Because smoke detectors reduce the risk of dying in a fire bu half,firefighters often provide audiences with information on how to install these protective decices in thier homes.  Specifically,they tell them these things: A smoke detector should be placed on each floor of a home.While sleeping,people are in particular danger of an emergent fire,and there must be a detector outside each sleeping area.A good site for a deterctor would he a hallway between living spaces and bedrooms.  Because of the dead-air apace that might be missed by not air bouncing around above a fire,smoke detectors should be installed either on the ceiling at least four inches from the nearest wall,or high on a wall at least four,but no further than twelve,inches from the ceiling.  Detectors should not be mounted near windows,entrance,or other places where frafts（过堂风）might direct the smoke away from the unit.Nor should they be placed in kitchens and garages,where cooking and gas fumes are likely to cause false alarms.

One responsibility of a firefighter is to（）.

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