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【简答题】
简述系统的定义、分类及特点。
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皮皮学刷刷变学霸
举一反三
【简答题】下列各分子中,中心原子在成键时以 不等性杂化的是A. B. C. D.
【简答题】( )首开人工喉的先河。
【简答题】根据下列设备图片,请选择出与远程家居控制系统相关的设备,在下列选项中正确的是A. B. C. D.
【单选题】Why， according to the passage， did ancient Chinese coins have a square hole in the center? 查看材料
A.
Because it would be easier to put them together and carry them around.
B.
Because it would be lighter for people to carry them from place to place.
C.
Because people wanted to make it look nicer.
D.
Because people wanted to save the expensive metal they were made from.
【单选题】Why， according to the passage， did ancient Chinese coins have a square hole in the centre? 查看材料
A.
Because it would be easier to put them together and carry them around.
B.
Because it would be lighter for people to carry them from place to place.
C.
Because people wanted to make it look nicer.
D.
Because people wanted to save the expensive metal they were made from.
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