题目

水果中含有不同的果酸，其中柠檬、柑橘等水果中含有柠檬酸，柠檬酸的结构式如下图所示。则下列关于柠檬酸的叙述中正确的是（    ）A．柠檬酸分子是由碳元素、氢元素、氧元素组成的B．柠檬酸中碳原子和氧原子的质量比为6:7C．柠檬酸分子含有6个碳原子、8个氢原子、7个氧原子D．一个柠檬酸分子中含有100个质子 第三部分：阅读理解（共15小题，每题2分，满分30分） 请认真阅读下列短文，从短文后各题所给的四个选项（A、B、C和D）中，选出最佳选项,并在答题卡上将该项涂黑。 A What to do if a fire starts? 　　Imagine it’s late at night. You hear the smoke detectors go off. You smell smoke when you wake up. Do you know what to do? 　　If a fire starts in your home, remember your escape plan and leave as quickly as possible. Keep the following things in mind to make a safe escape. 　　●Call“Fire!”to warn everyone in your family. 　　●If you know where the fire is, close as many doors as possible between you and the fire. 　　●If you’re in bed, roll out of bed and onto the floor. Crawl on the floor next to a wall. Being near the ground makes it easier to breathe. If possible, cover your mouth and nose with a wet cloth. 　　●Feel the entire surface of a door before you open it. If the door is warm or hot, do not open it. The fire is probably right outside your room. Find another way to leave the room. If the door is cool, open it a little. 　　●Look out and try to see the fire. If it is safe, leave the room. Remember to stay on the floor. 　　●If your clothes catch fire, stop immediately. Drop to the ground and roll. Remember: Stop, drop and roll. 　　●Call the fire department from outside and wait for help to arrive. 　56. What is the first thing you should do if a fire starts in your home? 　　A. Call the fire department.　　B. Call“Fire”to warn your family members. 　　C. Collect your favorite belongings to save from the burning house. 　　D. Have a white sheet from a window to let the fire department know where to go. 　57. What should you do if a fire starts and you are in bed? 　　A. Jump out of bed and run away.　　B. Roll out of bed and stand on the floor. 　　C. Stay in bed and then jump out of the window.　　D. Roll out of bed and onto the floor. 　58. What is not true according to the passage? A. Never go back into a burning building.　 B. If your clothes catch fire, stop moving immediately. 　　C. You should call the fire department before you leave the burning building. D. Cover your mouth and nose with a wet cloth if possible.