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问题 选择题

二氧化碳和氢气可在一定条件下反应，生成一种重要的化工原料甲醇：

CO2+3H2CH3OH+H2O。有关该反应的说法正确的是

A．钌-膦络合物的质量在反应前后发生了变化

B．氢原子数在反应前后发生了改变

C．属于复分解反应

D．体现了CO2的化学性质

答案

答案：D

题目分析：A选项因为是催化剂，故钌-膦络合物的质量在反应前后不变；B选项根据质量守恒定律可知，氢原子数在反应前后不变；C选项该反应不属于化合反应，因为氢气属于单质；D选项体现了二氧化碳的化学性质是正确的叙述．

填空题

Pentium微处理器在实模式下，最小的段只有　【5】　字节。
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单项选择题

Personal computers are used by one person at a time. The largest personal computer, or PC.S, can fit on a (1) . Some of these (2) have more than one microprocessor. (3) the primary processor, which is a general-purpose device, a PC may have one or more processors to (4) special kinds of work. Some machines, (5) , have maths processors, others have graphics processors to help process photographs and other illustrations. Still others have (6) processors.

Office workers also use PCS that are not (7) to a network. These machines are used for (8) tasks as word processing, performing financial calculations, and organizing and (9) bodies of information called databases. People use PCS at (10) for some of the same kinds of tasks. They use word processing programs for (11) communication, financial software for household budgets. Individuals also use their home computers to play (12) and to communicate (13) the internet.

Small, portable PCS are (14) with people who often work away from their desks. The (15) include laptop computers, which can be (16) on the lap; notebook computers, which are about the (17) of a loose leaf notebook; and palmtop, or handheld computers, which can be operated while (18) in the hand. Laptop and notebook computers have the same (19) as desktop computers. Palmtop computers have less power but still (20) some advanced capabilities. For example, they can process household financial data.

17（）

A.weight 

B.size 

C.length 

D.width
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