下列原因中不是引起电动机转动速度低于额定转速的是（）。
A、外部电路一相断线
B、鼠笼转子断条
C、绕线式电动机转子回路电阻过小
参考答案：C
The manager was worried about the press conference his assistant ________ in his place but，luckily， everything was going on smoothly.[ ]
A．gave
B．gives
C．was giving
D．had given
某理发店有这样一则广告“美丽从头开始”，给人耳目一新之感，请说说其中的妙处。
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