问题
单项选择题
对于同一电弧电源，当使用的负载持续率增大时，其许用电流应（）。
A、增加
B、减小
C、保持不变
D、不稳定
答案
参考答案：B
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对于同一电弧电源，当使用的负载持续率增大时，其许用电流应（）。
A、增加
B、减小
C、保持不变
D、不稳定
参考答案：B
“Ring… ring…” the telephone suddenly rang. Sam got up to the call. It was his aunt. “Sam, are you still at home?” she asked in surprise. Sam 1ooked at the clock. It was already 7:30 a. m. “Oh, my goodness! There’s an important today,” Sam shouted out. He hurried to wash his face and get .When he was going to leave the house, he remembered that he had not put away his books. He ran quickly to the door and put them into the bag. He then went to the bus stop to go to school as as she could. When he got into the classroom, his classmates were writing. “Why are you so ?” asked the teacher. ‘‘I’m sorry, sir,” Sam answered, afraid of looking down. “It was my clock. It failed to wake me up this morning and....” “Don't say anything about it,” his teacher him. “Don’t try to come late next time!” Sam said yes and walked to his quickly. But when he tried to do the paper, he could not think in a right way. He put his head on the desk and said, “What a day it has been for me!”
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