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问题 选择题

两个软塑料瓶中分别充满CO和CO2两种无色气体，下列试剂不能将二者鉴别出来的是

A．澄清石灰水

B．水

C．紫色石蕊试液

D．氯化钠固体

答案

答案：D

题目分析：物质的鉴别要根据现象来判断，CO具有还原性， CO2能使澄清石灰水变浑浊；二氧化碳与水反应生成碳酸，碳酸能使紫色石蕊试液变红。故选D。

单项选择题

As one works with color in a practical, or experimental way, one is impressed by two apparently unrelated facts. Color as seen is a mobile, changeable thing (1) to a large extent on the relationship of the color (2) other colors (3) simultaneously. It is not (4) in its relation to the direct stimulus which (5) it. On the other hand, the properties of surfaces that give (6) to color do not seem to change greatly under a wide variety of illumination color, usually (but not always) looking much the same in artificial light as in daylight. Both of these effects seem to be (7) in large part to the mechanism of color (8) .

When the eye is (9) to a colored area, there is an immediate readjustment of the (10) of the eye to color in and around the area (11) . This readjustment does not promptly affect the color seen but usually does affect the next area to which the (12) is shifted. The longer the time of viewing, the higher the (13) , and the larger the area, the greater the effect will be (14) its persistence in the (15) viewing situation. As indicated by the work of Wright and Schouten, it appears that, at (16) for a first approximation, full adaptation takes place over (17) time if the adapting source is moderately bright and the eye has been in (18) darkness just previously. Also, (19) of the persistence of the effect if the eye is shifted around from one object to another, all of which are at similar brightness or have similar colors, the adaptation will tend to become (20) over the whole eye.

15（）

A.transparent

B.succeeding

C.simultaneous

D.proceeding
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单项选择题

（）年，塘沽新港举行开港典礼，这是天津港由河港向海港转折的重要标志。

A.1952

B.1953

C.1954

D.1951
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