将一定量的金属钠放入一定物质的量浓度的NaOH溶液中，反应完成后，NaOH溶液的

如图表示的是细胞中含有的四种有机物的结构和功能。请据图回答：

(1)A是________，结构通式为_________，A形成E的方式为_________。

(2)图中F为________，这时B是_______，B有________种。

(3)图中G在植物体内主要是________，在动物体内主要是__________。

(4)图中H是_________。

(5)E在细胞内的合成受F、G、H中的_________控制。

设直线趋势方程的一般形式为=a+bt，其中表示销售额Y_t的趋势值，t代表时间序号(令2000年t=0)，而a与b的含义和计算公式是()。

A.A

B.B

C.C

D.D

普通混凝土防渗墙的水泥用量不宜低于( )。

A．80～100kg/m³

B．150～180kg/m³

C．200～220kg/m³

D．300kg/m³

For each blank, choose the best answer from the four choices and write down on the answer sheet.

(21) is a six bytes OSI layer 2 address which is burned into every networking

device that provides its unique identity for point to point communication.

(22) is a professional organization of individuals in multiple professions which focuses on effort on lower-layer protocols.

(23) functions with two layers of protocols. It can connect networks of different speeds and can be adapted to an environment as it expands.

(24) is the popular LAN developed under the direction of the IEEE802.5.

(25) is the popular backbone technology for transmitting information at high speed with a high level of fault tolerance which is developed under the direction of ANSI.

（23）是（）

A. The hub

B. The bridge

C. The router

D. The proxy

离心式压缩机的主要零部件有吸气室、叶轮、扩压器、弯道与回流器、蜗壳、密封装置、径向轴承、止推轴承及平衡盘。