Johnson—Laird等人（1972）的信封邮票任务实验是如何做的？能说明什么问题？
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等速移动定心夹紧机构是依靠定心夹紧元件做等速（）来实现定心夹紧的。
A. 运行
B. 交换
C. 旋转
D. 移动
The consequence of the three neutrality acts of the United States was（）
A. to make the United States gain time to arm itself
B. to actually help the aggressors by making clear that the United States would not intervene
C. to get the United States involved in the war
D. to prevent the United States form being dragged into the war
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