Listen! Joan ________ (sing) in the classroom.
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The girl ______ (like) wearing a skirt.
She __________ (wear) a red skirt now.
一个由线性电阻构成的电器,从220V的电源吸取1000W的功率,若将此电器接到110V的电源上,则吸取的功率为
A. 250W
B. 500W
C. 1000W
D. -1000W
理想电流源的外接电阻逐渐增大,则它的端电压
A. 逐渐升高
B. 逐渐降低
C. 先升高后降低
D. 恒定不变