关于声和电磁波的说法正确的是                      （     ）

   People know the dangers of fires. It's good for a family to learn how to prepare for a fire. Here are sonic suggestions:
Put a smoke a1arm in the house. Smoke from a fire causes the alarm to go off The alarm makes a loud sound. The sound tells everyone to leave the house at once.
   Make escape (逃脱) plans. They should know all the ways out of the house. If there is a fire, everyone follows the plan to get out. Part of the plan is to check all the windows to make sure they can be opened easily.
   Buy fire extinguishers (灭火器) in the house, Everyone in the family should know how to use them.
   Practise for a fire. They do fire practice because they teach children about fire safety. Everyone in. the family should know the following fire rules:
★ Don't open a hot door! The tire can grow more quickly if you open the door.
★Stay close to the floor! Smoke can be more dangerous than fire, The best air is near the floor because smoke rises.
★What will you do if your hair or clothes start to burn? First, stop! Don't run! The fire burns faster because of more air. Drop! Fall to the floor. Then roll! Turning over and over will make the fire go out. Put a blanket (毯子) around you to keep air away from the fire that may still be on you.
   There are many possible causes for fires. A wise family is ready all the time. If there is a fire, don't forget to call 119 for help

克里木战争对俄国历史发展的最大影响是（  ）

下列关于人和被子植物结构层次的叙述，正确的是（   ）