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参考答案：[*]
解析：本题考查极限的基本计算，涉及变限积分的换元法和求导等知识点，是一道具有一定综合性的基础题． [*]
I'm sorry, but I'm too busy to help you now. I can only do one thing .[ ]
A. at one time
B. at a time
C. at time
D. at the time
联轴器端面应平整，圆周应（）现象。
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