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标题: Lsat questions, need help [打印本页]

作者: workhard77    时间: 2002-10-13 23:35     标题: Lsat questions, need help

14. Cafieine can kill or inhibit the growth of the larvae of several species of insects. One recent experiment showed that tobacco hornworm larvae die when they ingest a preparation that consists in part of finely powdered tea leaves which contain caffeine. This result is evidence for the hypothesis that the presence of non-negligible quantities of caffeine in various parts of many diverse species of plants is not accidental but evolved as a defense for those plants.

The argument assumes that

(C) caffeine-producing plants grow wherever insect larvae pose a major threat to indigenous plants or once posed a major threat to the ancestors of those plants

(E) caffeine-producing plants or their ancestors have at some time been subject to being led upon by creatures sensitive to caffeine

--------------Why E is right and C is not right?

17. A new silencing device for domestic appliances operates by producing sound waves that cancel out the sound waves produced by the appliance. The device unlike conventional silencers actively eliminates the noise the appliance makes and for that reason vacuum cleaners designed to incorporate the new device will operate with much lower electricity consumption than conventional vacuum cleaners.

Which one of the following if true most helps to explain why the new silencing device will make lower electricity consumption possible

(A) Designers of vacuum cleaner motors typically nave to compromise the motors' efficiency in order to reduce noise production

(B) The device runs on electricity drawn from the appliance's main power supply

----------Why B is not right?
作者: zyh79    时间: 2002-10-14 00:52

1.结论:植物所含Cafieine的多少不是偶然的,而是自身防御能力的进化。
  缺这样的假设:这些植物或其祖先曾经受制于对Cafieine敏感的幼虫,所以,为了让自己存活下来,只有增加自己的Cafieine来毒死这些虫子。
  c答案中的insect larvae是不是对Cafieine敏感的虫子,不知道
2。b说装置耗的电算在家用电器提供的总耗电里,没有提供与原家用电器的比较。
   如果原家电没装置,现在更耗电;如果原家电有,谁大谁小,不知道
作者: workhard77    时间: 2002-10-14 11:09

2.可是正确答案A中也没有与conventional silencers进行比较啊?
作者: zyh79    时间: 2002-10-14 13:03

怎么没比较?
不是说了把马达的功效降低的吗。
嘿,功效(功率)小了,更省电。
作者: Kilroy    时间: 2002-10-14 13:08

这道题还牵扯到中学物理常识,不知道老美是否做的出来?
作者: workhard77    时间: 2002-10-15 12:16

Got it. Thank you!




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