造成逆变失败的原因有（）、（）、（）、（）等几种。
参考答案：逆变桥晶闸管或元件损坏；供电电源缺相；逆变角太小；触发脉冲丢失或未按时到达
用括号内所给动词的正确形式填空。
1. When I was young, my grandfather told me that the sun (rise) in the east.
2. The boy (take) to hospital at once after he fell off the tree.
3. — You forgot (close) the window again.
— Really? I won't next time.
4. We hope that more charity shows (hold) to raise money for Project Hope.
5. John (chat) with his son while his wife was cooking in the kitchen.
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