题干

如图所示是一个咖啡磨。陈晓丽同学在使用中发现摇动手柄时常常打滑。为修理改咖啡磨,她进行了以下工作,其中明确进行系统分析的是(   )

A:给咖啡磨加润滑油

B:拧下螺帽,更换手柄

C:打开外壳,更换齿轮

D:根据咖啡磨各组成部分的功能和联系来研究打滑的原因

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答案(点此获取答案解析)

D

同类题2

Canada Day

                                                                  

                                                                                                                              

      Since 1982, July 1st has been officially known as Canada Day. Canadians of all ages take part in this festival across the country.
  Canada Day is the year's biggest national party. In many towns and cities, the government organizes a lot of events, often outdoors. These include parades(游行), concerts, festivals, firework displays and ceremonies for new Canadian citizens(公民). The celebrations often have a patriotic mood. Canada's national flag, a symbol for Canada Day, can be seen everywhere and a lot of people paint their faces red and white, which are Canada's national colors. The celebrations in Ottawa, Canada's capital city, are especially grand and exciting.
  In the province of Quebec, many home rentals(租赁)start on July 1st and last for exactly one year, and many people in Quebec spend Canada Day moving from one house to another. So in Quebec, Canada Day is also known as Moving Day.
  Many organizations, businesses and stores are closed this day. Only some bookstores, ho spitals and gas stations may be open. Post offices are closed, too. As Canada Day falls in the Canadian summer holiday period, all schools are closed as well. In some areas, special services are provided for large events. The concerts, parades and festivals may cause some traffic jams.