什么是手动操作方式（MAN UNL）？

My grandma_____in the country. Now she   in the city.

A．used to live, lives

B．used to living, lived

C．uses to live, is living

D．was used to live, lives

An internet is a combination of networks connected by (1).When a datagram goes from a source to a(2)，it will probably pass many (3)until it reaches the router attached to the destination network. A router receives a (4)from a network and passes it to another network. A router is usually attached to several networks. When it receives a packet, to which network should it pass the packet? The decision is based on optimization: Which of the available (5)is the optimum pathway?

空白（1）处应选择（）

A.modems

B.routers

C.switches

D.computers

简述烟气中有害物质的类别。

A．把你的详细地址B给我，C邮件到来我D给你送过去。

A．好

B．好

C．好

D．好

《安全色标准》中，表示警告、注意的颜色为（），表示禁止、停止的颜色为（），表示指令、必须遵守的颜色为蓝色。