失步保护应能正确区分（）所处的位置，在机组进入失步工况时发出失步起动信号。
参考答案：失步振荡中心
用所给单词的正确形式填空。
1. These _______ (be) pencils.
2. Is it _______ (she) marker?
3. Our classroom ________ (have) two doors.
4. It's a ________ (wind) day today.
5. The girl is the ________ (one).
6. I ________ (work) hard at school.
7. Jack is ________ (write) on the paper.
8. What ________ (be) they?
9. The ________ (leaf) on the trees are yellow.
10. The wind is ________ (blow) the tree's leaves.
闭合电路的电流，与电源电动势成正比，与整个电路的电阻成反比。
