中性点不接地系统，发生单相接地可继续运行，但持续时间不超过5小时。
A. 对
B. 错
电能质量最主要的是指频率、电压、谐波三个方面的问题。
A. 对
B. 错
In this class, some of my classmates ________ English very well.
A. spoke
B. is spoken
C. will speak
D. speak
If you still ________ your money in such a free way, it ________ be long before you ________ the heritage (遗产).
A. spend; won't; run out of
B. will spend; don't; run out of
C. spend; won't; will run out of
D. will spend; don't; will run out of
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