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问题 选择题

下列变化中，不属于缓慢氧化的是（　　）

A．动物呼吸

B．酒的酿造

C．铝在氧气中燃烧

D．食物腐败

答案

A、动植物呼吸作用是动植物与空气中的氧气发生的不容易察觉的缓慢氧化，故选项错误．

B、酒的酿造是粮食等与空气中的氧气发生的不容易察觉的缓慢氧化，故选项错误．

C、铝在氧气中燃烧，属于剧烈的氧化反应，故选项正确．

D、食物腐烂属于氧化反应，但是比较缓慢，属于缓慢氧化，故选项错误．

故选C．

单项选择题

As Philadelphia grew from a small town into a city in the first half of the eighteenth century, it became an increasingly important marketing center for a vast agricultural hinterland. Market days (1) the crowded city even more crowded, as farmers from within a (2) of 24 or more kilometers brought their sheep, vegetables, cider and other products for direct sale to the (3) . The High Street Market was continuously (4) throughout the period until 1736, (5) it (6) from Front Street to Third. By 1745 New Market was opened on Second Street. The next year the Callow Hill Market began (7) .

Along with market days, the (8) of twice-yearly fairs persisted in Philadelphia (9) after similar trading days had been discontinued in other colonial cities. The (10) provided a means of bringing handmade goods from (11) places to would-be buyers in the city. Linens and stockings from Germantown, (12) , were popular items.

Auctions were another popular (13) of trade. Because of the competition, retail (14) opposed these as well as the fairs. (15) governmental attempts to eradicate fairs and auctions were less than successful, the ordinary (16) of economic development was on the merchants’side, as increasing business specialization became the (17) of the day. Export merchants became differentiated from their importing counterparts, and specialty shops began to appear (18) general stores selling a variety of goods.

One of the reasons Philadelphia’s merchants prospered was because the surrounding area was undergoing tremendous economic and demographic growth. They did their business, (19) , in the capital city of the province, (20) to not only the governor and his circle, but citizens from all over the colony.

15（）

A. Now that

B. Since

C. Although

D. If
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单项选择题

实验表明，包橡皮布后的橡皮滚筒在平面上受压滚动时，它和平面的接触长度（）。

A.变长

B.变短

C.不变

D.不确定
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