类推的思维方法在化学学习和研究中常会产生错误的结论，因此类推_爱下问搜题

搜题请搜索小程序“爱下问搜题”

问题单项选择题

类推的思维方法在化学学习和研究中常会产生错误的结论，因此类推出的结论最终要经过实践的检验才能决定其正确与否。下列几种类推结论中不正确的是______

A．Mg失火不能用CO₂灭火；Na失火也不能用CO₂灭火
B．Fe₃O₄可写成FeO·Fe₂O₃；Pb₃O₄也可写成PbO·Pb₂O₃
C．能用电解熔融NaCl来制取金属钠；也能用电解熔融MgCl₂来制取金属镁
D．Fe与S直接化合生成FeS；Al与S直接化合也可以得到Al₂S₃

答案

参考答案：B

解析： Fe为ⅧB族元素，可显+2、+3价，而Pb为ⅣA族元素，显示的是+2、+4价，写成PbO·Pb₂O₃不合适。

完形填空

Many people think that Americans 21 their cars almost more than anything else. When 22__ people are fourteen years old, they want to have their __23_ cars. They don’t ask for a car from their 24__. So many of them work in _25_ time during their last year of high school to buy a car. Learning to 26 _ and getting a driver’s license may be one of the most exciting things in a young person’s life.
Some people almost 27 _ go to a doctor when they are ill. But they will __28_ their cars to a garage as soon as they think there is a 29 . On Saturdays or Sundays some people may 30 most of their time washing and repairing their cars.

小题4:A, friends B. teachers C. parents D. brothers

单项选择题

使用反切断刀，适用于切断（）。

A．硬材料

B．软材料

C．细长轴

D．大直径工件