电力系统中实现频率和有功功率自动调整的方法有哪几种（）。
A. 有差调频法
B. 主导发电机法
C. 积差调频法
D. 改进积差调频法
E. 分区调频法
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When did ants first appear on the earth?
Please explain why the savagery of the soldier ants is a legend in Africa.
What is an ants’ nest like in structure?
How is a Queen ant different from ordinary ants?
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