【单选题】
A点坐标为（10、20、30），B点坐标为（30、20、30）则AB距离为______。
①
Normal
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7.8 磅
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ZH-CN
X-NONE
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②
Normal
0
7.8 磅
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2
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EN-US
ZH-CN
X-NONE
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③
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④
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0
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铅垂线
【单选题】
在单级中断系统中，CPU一旦响应中断，则立即关闭________标志，以防止本次中断服务结束前同级的其他中断源产生另一次中断进行干扰
①
中断允许
②
中断请求
③
中断屏蔽