题干

如图所示,利用维生素C能使淀粉-碘溶液退色的性质,可以比较苹果汁和橙汁中维生素C含量的多少。要得出正确结论,实验过程中不需要进行控制的条件是(  )

A:胶头滴管滴出的果汁的滴数必须相等

B:烧杯中的淀粉-碘溶液的质量必须相等

C:胶头滴管滴出的每滴果汁的体积必须相等

D:烧杯的大小必须相等

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答案(点此获取答案解析)

D

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阅读下列短文,从每题所给的A、B、C和D项中,选出最佳选项。

      When one of your car tires goes flat, there are two things you can do, you can complain and change it or, if you don't have a spare, stand helplessly beside the road and hope someone comes to your rescue. Now comes a third choice, called Quick wheel. It is designed to get disabled motorists rolling again as quickly as possible.

      Quick wheel is basically a tiny emergency trailer-complete with three tough little wheels of its own-that supports the flat tire and enables the motorist to drive to a service station without losing much time or expending much energy. The product is made in the Netherlands but is owned and marketed by a US company, Quick wheel Inc. of Greenwich, Connecticut. According to the firm's president, Robert Bockweg, the product meets each of the major worries that customers relate with flat tires: safety, lost time and physical labor.

      To use it, motorists simply unfold the product to its fully extended position, set it in front of the disabled tire, drive the car onto the Quick wheel's ramp(斜板) and fix a special safety strap over the tire. The tire is then locked, or cradled, in Quick wheel's metal frame. Its three wheels do the rest of the work. According to Quick wheel Inc, its product can be driven "for miles" at the speed of up to 45 miles per hour "without any noticeable change in the vehicle's braking (车辆刹车) or steering operation". The company also says that it can be used on just about any type of car, jeep, mini-van or trailer (拖车).

      Bockweg says that Quickwheel will be sold first in the United States, at a price of $150. Sales agreements now being talked over should make the product ready for use in Japan, Canada and Western Europe in the near future. (words: 314 ; time :5ms)