下列做法中符合安全用电原则的是( )
A:使用测电笔辨别火线或零线时,手不能接触笔尾金属体
B:发现有人触电,立即用手将他拉开
C:家庭电路中,用电器的开关可以任意安装在火线或零线上
D:家用电器的金属外壳一定要接地
如图,甲乙两个相同的枝条,将乙的叶片全部摘除后,同时插入两个装有红色溶液的烧杯中,下列分析正确的是( )
Many Chinese people have a good time during the Chinese New Year. It usually comes in January or February. Each year gets a name. It may be called the year of the dog or the year of the tiger instead of (代替)2006 or 2010. Usually there is dragon(龙)dance in the street. The dragon is a strange(奇怪的)animal about 20 feet(英尺)long. It is made of paper and cloth(布). Men hide(藏)under the dragon, and make a lot of noises by shouting and laughin9. There are always a lot of fireworks(烟火). After the dragon dance, the children sing and dance in the street.