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问题 填空题

鸡、兔若干，关在同一个笼中，头有30个，腿有84条，若设则鸡有x只，兔有y只，则列方程组为：______．

答案

鸡有2条腿，兔有4条腿．

列方程组为

x+y=30
2x+4y=84
．

单项选择题

A work authorization system can be used to______.

A) manage who does each activity
B) manage what time and in what sequence work is done
C) manage when each activity is done
D) manage who does each activity and when it is done
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单项选择题 A1/A2型题

下列各项中，不属于三棱针法的适应证是（）

A.痤疮

B.丹毒

C.寒痹

D.中暑

E.湿疹
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