标题: L 19-3-14 [打印本页]
作者: asasasas1 时间: 2004-9-28 12:12 标题: L 19-3-14
14. Caffeine 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
(A) caffeine-producing plants are an important raw material in the manufacture of commercial insecticides
(B) caffeine is stored in leaves and other parts of caffeine-producing plants in concentrations roughly equal to the caffeine concentration of the preparation fed to the tobacco hornworm larvae
(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
(D) the tobacco plant is among the plant species that produce caffeine for their own defense（E）
(E) caffeine-producing plants or their ancestors have at some time been subject to being fed upon by creatures sensitive to caffeine
What the meaning of E? What's the meaing of " been subject to being fed upon"?
作者: linsonstudy 时间: 2004-9-29 13:19
which is the answer to this question?
be subject to :受制于...的, 受...影响的, 以...为条件的
feed on: 以什么为食
the meaning of this sentence: 生成咖啡因的植物或其祖先有时受到以它们为食并且对咖啡因敏感的生物的影响。
| 欢迎光临 国际顶尖MBA申请交流平台--TOPWAY MBA (http://forum.topway.org/) |
Powered by Discuz! 7.2 |