豌豆起源于哪里?有哪些别名?什么时候怎样传入中国?
The lower end of each piston rod is reduced in diameter to fit a bore in the (), this being secured to the piston rod by a nut.
A. piston gudgeon pin
B. piston skirt
C. cross-head
D. cross-head pi
根据GB/T12241-2005《安全阀一般要求》的规定:关于安全阀设计、材料和结构的哪种说法是错误的()
A. 安全阀应设有导向机构以保证动作和密封的稳定性
B. 阀座和阀体应做成一体,防止运行时松动
C. 对于有毒和可燃介质的安全阀应为封闭式
D. 应对所有外部调节机构采取上锁或铅封措施
You download a file from an FTP site on the Internet. What is the highest layer in the OSI model used in this FTP operation?()
Application
B. Presentation
C. Session
D. Transport
E. Internet
F. Data Link
G. Physical