（）是指国家在一定时期内生产的最终产品和服务按价格计算的货币价值总量。 A.总需求

优质碳素钢经调质处理制造的轴，验算刚度时发现不足，正确的改进方法是（）。

A、加大直径

B、改用合金钢

C、改变热处理方法

D、降低表面粗糙度值

从组展商的主要收入来源可看，会展产品定价工作主要涉及（）。

A.展位价格

B.广告价格

C.赞助价格

D.入场卷价格

经常被用来辨别方向的北极星是属于（）。

Both bus and tree topologies are characterized by the use of multipoint (1).For the bus, all stations attach, through appropriate hardware (2) known as a tap, directly to a linear transmission medium, or bus. Full-duplex operation between the station and the tap allows data to be transmitted onto the bus and received from the(3). A transmission from any station propagates the length of the medium in both directions and can be received by all other  (4). At each end of the bus is a (5) , which absorbs any signal, removing it from the bus.

空白（3）处应选择（）

A.tree

B.bus

C.star

D.ring