单项选择题

Questions 16-20 are based on the following passage:
  Firefighters are often asked to speak to school and community groups about the imprtance of fire safety.particularly fire prevention and detection.Because smoke detectiors reduce the risk of dying in a fire by half,firefighters often provide audience with information on how to install these protective devtces in their 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 dectector outside each sleeping area.A good site for a detector would be a hallway that runs between living spaces and bedrooms.
  Because of the dead-air space 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 nearnest 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 drafts（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.
 

 

Compared with homes without smoke detectors,homes with them give their owners a 50% better chance of（）.

点击查看答案&解析