我国文献所知最早的确切年代是()
A.公元前1250年
B.公元前1046年
C.公元前841年
D.公元前771年
参考答案:C
— The iPhone 4s has been on the market for some time. Have you got one?
— Yes, I________one during my visit to Hong Kong. [ ]
A. have bought
B. bought
C. had bought
D. would buy
起重机械安全规程要求:跨度等于或超过40m的装卸桥和门式起重机,应装( )。
A.上升极限位置限制器
B.运行极限位置限制器
C.偏斜调整和显示装置
D.缓冲器