用来供给断路器跳闸，合闸和继电保护装置工作的电源有（），（）两种。
参考答案：直流；交流
根据句意和首字母提示完成下列单词。
1. Look! The children are playing soccer on the p_______.
2. W_______ is between Tuesday and Thursday.
3. Most of students like playing computer g_______.
4. What about s_______ English after class?
5. The girl is reading the school newspaper with great i_______.
6. The Great Wall is b_______. I want to go to the Great Wall.
如何降低泥浆比重？
