中性点接地，设备外壳（）的运行方式叫保护接零。
A.接地
B.接地或接零
C.接中性线
D.接负载
参考答案：C
成煤有哪些必要条件？
用所给单词的正确形式填空。
1. There is not much _____ (pollute) in Nanjing.
2. I would like to live in tall _____ (build) because we can be close to our friends.
3. KFC and McDonalds are famous _____ (west) restaurants.
4. I go swimming in summer when it's warm and _____ (sun).
5. A _____ (cash) is a man who collects money and pays the change back in a shop.
