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【多选题】
输入交流电抗器为另购件,在以下情况下应考虑接入交流电抗器:A.
①变频器所用之处的电源容量与变频器容量之比为10﹕1以上；
B.
② 同一电源上接有晶闸管变流器负载或在电源端带有开关控制调整功率因数的电容器；
C.
③ 三相电源的电压不平衡度较大（≥3%）；
D.
④变频器的输入电流中含有许多谐波成分，这些谐波电流都是无功电流，使变频调速系统的功率因数降低到0.75以下
E.
⑤变频器的功率<30kW。< /div>
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A.
George is going to stopping working in the summer.
B.
George can go to a school in the summer.
C.
George cannot work and study at the same time.
【单选题】听力原文：M: Do you want your television repaired? W: Yes, but not by the place you recommended. M: Why not? The repairmen are very good and the charges are so reasonable. W: That may be, but I couldn't fi...
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It needed fixing.
B.
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C.
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D.
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A.
空、回肠之间无明显界限
B.
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C.
回肠黏膜皱襞明显，数量多
D.
空肠一般位于左上腹
E.
空肠续于十二指肠
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A.
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B.
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C.
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D.
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【单选题】As soon as all the chairs are _______, we can let the people _______ outside enter.
A.
in the place; waiting
B.
in place; waiting
C.
in the place; waited
D.
in place; waited
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