钢与铁有何区别?
参考答案:
区别在于含碳量不同:
含碳量在0.04--2%的称为钢
含碳量大于2%的称为铸铁.
含碳量小于0.04%的称为工业纯铁。
You'd better keep the window___. It's so hot here.[ ]
A. open
B. opens
C. opened
D. opening
办公自动化怎样实现?