问题
选择题
— Now, where is my purse?
— _____! We'll be late for the picnic.[ ]
A. Take your time
B. Don't worry
C. Come on
D. Take it easy
答案
答案:C
— Now, where is my purse?
— _____! We'll be late for the picnic.[ ]
A. Take your time
B. Don't worry
C. Come on
D. Take it easy
答案:C
下表列出了常见几种合金的成分及主要性质
名称 | 高速工具钢 | 武德合金 | 镍铬合金 |
成分 | 铬3.8~4.4% 钨11~19%、钒等 | 铋50%,铅25%, 锡、铬 12.5% | 镍80%,铬20% |
性质 | 耐磨,硬度大 | 熔点很低(70℃) | 熔点高,电阻大 |