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
