When released into the atmosphere, the refrigerant Freon damages the Earth’s ozone layer. A new kind of refrigerant does not have this effect. The manufacturer claims that replacing Freon with the new refrigerant in both new and existing refrigerators will prevent any further Freon damage to the ozone layer apart from that being done by the Freon already in the atmosphere. Which of the following must be true if the manufacturer’s prediction is to prove accurate
A. Freon can be replaced with the new refrigerant without releasing any Freon into the atmosphere.
B. The damage already done to the ozone layer is not of environmentally significant proportions.
C. The atmosphere can reverse the damage to the ozone layer caused by the past use of Freon.
D. The new refrigerant can counteract the damaging effects of Freon on the Earth’s atmosphere.
E. (E) The new refrigerant causes no environmental damage of any kind when it is released into the atmosphere.
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无论什么样的计算机系统在调度作业的时候必须遵循—必要条件，即______。
Biometric access-control systems—those using fingerprints, voiceprints, etc., to regulate admittance to restricted areas—work by degrees of similarity, not by identity. After all, even the same finger will rarely leave exactly identical prints. Such systems can be adjusted to minimize refuels of access to legitimate access-seekers. Such adjustments, however, increase the likelihood of admitting impostors. Which of the following conclusions is most strongly supported by the information above
A. If a biometric access-control system were made to work by identity, it would not produce any correct admittance decisions.
B. If a biometric access-control system reliably prevents impostors from being admitted, it will sometimes turn away legitimate access-seekers.
C. Biometric access-control systems are appropriate only in situations in which admittance of impostors is less of a problem than is mistaken refusal of access.
D. Nonbiometric access-control systems—based, for example, on numerical codes—are less likely than biometric ones to admit impostors.
E. (E) Anyone choosing an access-control system should base the choice solely on the ratio of false refuels to false admittances.
Essentially all polar ice forms from precipitation that falls as snow. Extremely cold air cannot hold much moisture and consequently cannot produce much snowfall, in recent years, air masses in both polar regions have been, without exception, extremely cold. The information above most strongly supports which of the following conclusions
A. If polar ice is currently growing and expanding at all, it is doing so only slowly.
B. If air temperatures in the polar regions were considerably warmer, much polar ice would melt off.
C. In the last few years, snowfall in the polar regions has been virtually continuous.
D. The thicker the polar ice is, the colder the air masses that are in contact with it.
E. (E) For snow to turn into ice in the polar regions, the air has to be extremely cold.
表面被光亮的金黄色茸毛
A. 狗脊
B. 大黄
C. 川乌
D. 白芷
E. 黄芩
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