如图所示，小明同学仔细观察三只插脚，有了新的发现：标有“E”字的插脚比其他两脚稍长一些．他又查看了其他家用电器的三脚插头，也是这种情况．它比其他两脚稍长一些，有什么好处？
答：标有“E”字的插脚为接地线，比其它两脚稍长一些．这样插插头时能使家用电器的金属外壳先接地，拔插头时能使金属外壳后离开地线，即使家用电器因绝缘不好“漏电”，也会使电流通过导线导入大地，人也就不会触电．
| 根据下面每段话的陈述内容，从方框中选出各段恰当的主题，并将其字母序号填入题前括号内。 | |
Each plastic bag takes more than 1,000 years to disintegrate (粉碎) and never completely disappears. ( )2. When I was young, I thought space was wonderful. I spent all day imagining that I had my own spaceship. I would invite my cousins and my friends to join the trip and spend the whole day exploring other planets. That was my earliest dream. ( )3. In Brazil, people wear white clothes on New Year's Eve (31 December) because it brings good luck. At midnight people go to the sea and jump over the waves seven times. Then they throw flowers into the sea and make wishes for the New Year. ( )4. Over hundreds of years the Earth gets hotter and then it gets colder again. But scientists are sure that what' s happening now is different. The world is getting warmer. For example, the way we use energy from coal and oil is making the planet hotter. This is one cause of climate (气候) change- it's man-made. ( )5. Sometimes, good things happen because of mistakes. Once I got on the wrong train. That was a big mistake. But I saw a good friend on that train. I was glad I made that mistake! When a good thing comes out of a mistake, that's a happy accident. |