安定性试验的沸煮法主要是检验水泥中是否含有过量的（）。
A、氧化钠；
B、三氧化硫；
C、游离氧化镁；
D、游离氧化钙；
参考答案：D
—_____do you have a class meeting?
— Once a week.
A．How long
B．How often
C．How soon
D．When
For each blank, choose the best answer from the four choices and write down on the answer sheet.
（）is a channel’s capacity which directly reflects the data transfer rate of the channel.
（）functions in a NetWare network which is used to define addressing schemes.
（）is a network layer device that supports multiple LAN interfaces and segments LANs into smaller collision and broadcast domains.
（）is the popular LAN developed under the direction of the IEEE802.3.
（）is a device which enables digital microcomputers to communicate across analog telephone lines.
A．Token Ring
B．Token Bus
C．Ethernet
D．FDDI
