单项选择题

In this part there are three passages and one table. each followed by five quesrions or unfinished statements. For each of them, there are four choices marked A. B. C and D. Choose the best one and mark your answer on the ANSWER SHEET with a single line through the center.
11-15

Firefighters ane often asked to speak to school and community groups about the importance of fine safety, particularly fire prevention and detection. Bccause smoke detectors reduce the risk of dying in a fire by half. firefighters often provide audiences with information on how to install these protectivc devices in their homes. Specifically, they tell them these things: A smoke detector should be placcd on each floor of a home. While sleeping, people are in particular danger of an emergent fire、 and there must he a dctcctor outside each sleeping area. A good site for a detecior would he a hallway that runs between living spaces and bedrooms. Because of the dead-air space that might be missed by hot air bouncing around above a fire, smoke detcctors 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. Deteccors should not be mounted near windows, entrances, 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.

One responsibility of a firefighter is to（）.

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