The reason _____ I'm writing to you is to tell you about a party on Saturday.
A. because
B. why
C. for
D. which
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The film is set in the period _____ the divide between rich and poor was greater than it is now.
A. where
B. when
C. which
D. why
电阻元件的电压电流相位关系是()。
A. 相位相同
B. 电压超前电流90°
C. 电流超前电压90°
D. 不确定
自感系数为L=0.01h的电感在交流电路中的感抗为3.14欧姆,该电路的频率大小为()。
A. 60HZ
B. 50HZ
C. 100HZ
D. 400HZ
配送是作()的移动。
A. 长距离、大量货物
B. 长距离、少量货物
C. 短距离、大量货物
D. 短距离、少量货物